Help, what are we doing wrong?

We are having problems keeping acroporas and bird's nest in our tank... We went to the GIRS reaf show, and after having two other bird's nest die in our tank, we were talking to this dealer (first one to the left when you walk in) and he said that this "ora bird's nest" was the easiest of the bird's nest to keep. It was also the best "starter nest". He said that lighting and flow were not nearly as huge of an issue making this one easier to keep. We bought it and it was doing beautifuly for about 3 weeks and now it's turning white. Just like all of our other ones...3-4 weeks, tops. The next weekend, we found a reefer that was getting out of the hobby and bought a beautiful regular birds nest (the green and tan ones) that was huge and some acroporas also. They are all turning white now also. We have tried moving them, adjusting flow towards/around them, put them high in the tank, low in the tank, mid tank, everything that we can think of! The guy that was shutting down his tank had sold us a green staghorn frag, a green slimer frag, a purple staghorn (entire coral) and a tricolor valadia (??) along with the big birds nest. They all looked beautiful and healthey in his tank. The green staghon frag is still doing alright, along with the slimer and valadia. They do not look as nice in our tank as they did in his, but they are not white either/DesktopModules/ActiveForums/themes/_default/emoticons/smile.gif the purple staghorn is completely white, we fragged off two good branches when we noticed it was turning white and those died the next day also. The big birds nest along with the ora birds nest are slowing turning more and more white each day...what are we doing wrong? Pollyps (many different kinds), xenias, zoos, mushrooms, candy cane corals, chalise, pocillapora, hydnophora horn coral are all doing great and seem to love our tank. Just to be clear, we are not blaming the people that we got these corals from, we know it is our tank, we just don't know what is wrong with our tank...
Our stats: 55 gal- filtered (not sumped)
20K halide
mag: 1200-1250
cal: 520-540
kH: 125.3
nitrite: 0
nitrate: 10- we did notice this...its normally 0 and we are using a nitrate reducer to lower it.
pH 8.2
RO system for water
Reef Crystals for salt
We are feeding/adding different things like Black Powder (they love that stuff), reef snow, phyto feast, oyster feast, reef prime, Kent marine essential elements, phyto plex and some others.  We do target feeding with all of our corals also.
We are still "new" to this hobby, greatly adore it, but are frustrated that we can't keep some of these corals.
Any help would be greatly appreciated!

 

Sorry, we do have the duo-backpack skimmer- I'm sorry, my other half usually deals with stuff so I'm not sure of the exact name of the skimmer. Now that I am looking through our test kit notes, it looks as though right after we went to the show, which I believe was the 15thish???, our calcium was at 460 and the alkalinity was at 11. We did not have the magnesium kit then. on May 24th, calcium was 560, then we got the magnesium test kit and that started at 1100, went to 1150 the next day and calcium at 520. Now are magnesium is up to 1200 and calcium to 540.
Our tank is about 8 months old, started adding corals (all the ones that like our tank) about 6 months ago.
I am not sure what the autotopoff is but I am pretty sure we do not have one
What do recommend for lowering calcium and rasing alkalinity?
Is it possible that we added to much all at once? We are wanting a bigger tank, Girs has recommended holding out for 120g for our 4 ft space. Will that help?

 

Which foods do you all recommend? We don't add all of them at the same time, we mix it up. Should we only use a couple of them and keep in consistent? We were using different ones because it was recommended to us by different sites and our pet stores. I will try anything to save these corals and get this figured out. I replied to another post, but you might not have seen it yet, we do have a "duo-backpack skimmer" (I think that is what its called). And the tank has been up for 8 months. Thanks again for all of your help!!!

 

The first day that it got very hot, our tank did hit 85 degrees, but we got it back down to 82 degrees that same day. We do not have a chiller on it (have thought about it but can't afford it), but have figured out a fan method of when to turn the fan on and off with the lights. Over the last week, the tank has stayed between 79 and 81 degrees consistently. The lights are on from noon-9pm everyday. Would the temp swing from that one day have hurt them enough to bleach them all out? I am not familiar with reef chemistry calculator yet, my fiance might be but I have not heard him talk about it yet. I will look into that after I post this, but I will probably have more questions about that/DesktopModules/ActiveForums/themes/_default//emoticons/smile.gif Thanks everybody!!!
Also, how do you go about letting the calcium lower itself?
I just remembered this, right after we added the corals from the coral show, our tube amenonme released itself from its tube and landed on our carpet amenome (they are no separate ends of the tank). Both survived and were doing fine, we did a major water change, which I'm sure wasn't great for the new corals but we thought it was needed due to them "raging war on each other". Would that have set all the corals up to fail? But we didn't add the acrapora and other birdsnest until the next weekend...

 

We do not have alot of shrooms and zoas, just a couple of small rocks with some on them. Counting I would say 8-10 mushrooms tops, and 3 small collonies for Zoa with 10-15 each. Is that considered "tons"? From other tanks that we have seen, I guess I would say that we have very few compared to some other people. And what do you mean by do we "run carbon"? We have carbon filters in our filter system...

 

Ammonia was 0 and the hallide was just changed last month.

 

mthomp: Our filter system is the emperor 400. It does have wheels at the top. So you recommend making our own filters? We went to a aquatic shop in omaha and they recommended the same thing. They said that if they knew you had a saltwater tank, they would refuse to sell a pre-made filter. They insisted on buying the carbon and making your own. The aquatic shops in Des Moines do not necessarily agree and do not sell just carbon. We are not dosing calcium besides what comes with a water change with the reef crystals. Out SG is consitanty at 1.025. Due to evaporation we add 1-2 gallons of RO water everyday to every other day. This is not salt mixed. We only add the salt mixed water during an actual water change.
I am interested to know more about your tank since it sounds similar to ours. What do you feed? What do you use to keep your levels consistent? what salt do you use? Do you think that the phyto is adding elements that we do not need?
Thanks again for everybody's help!

 

So what would probably be best would be to let these guys die out, or just take them out all together, and let what is living and thriving do its thing until we get more experienced? That is not the answer that I wanted/DesktopModules/ActiveForums/themes/_default//emoticons/sad.gif But I do understand why you say that. We do really like the birds nest, hence why we keep trying them. We had gone awhile with out them and were holding out for the show, we thought for sure that we had it figured out and in all actuallity, I think we did have it figured out for what we had/have. We were very excited about the ORA birdsnest because it was "easier to keep" but obviously, not easy enough. I am learning that this a patient hobby/DesktopModules/ActiveForums/themes/_default//emoticons/smile.gif