birds nest problems

I have a 55 gal set up with a dual cpr back pack skimmer and a metal halide with 15k bulbs i have a bunch of different corals in there from carnations metallic star polyps tube anemone bunch of xenias a loco lobo leather 2 birds nests a soft tree coral and a brain coral rock and a frogspawn and some other things i cant think of right now.  Anyways im having problems keeping my birds nest alive, my salinity is at 1.025 ph 8.4 alkalinity 440 around that calcium is upwards of 560 and i have both birdsnest way up high in the tank everything i try i cant keep them alive they start bleaching away from the bottom upwards i will pull them out and put them in a bag of tank water and put about 10 drops of iodine in with them and let them sit for about 10 mins and that still doesnt do anything. any ideas?

 

My phosphate is 0 I have tried to put them half way up in the tank and they seem like they bleach faster then when they are at the top, I have a pretty good current flowing on them both and they are in their only spot in the tank I don't have any other corals anywhere close to them

 

I have tried everything possible that I know of with them at the top of the tank the bleaching has slowed down alot, but after 2 weeks or so you will notice more on the branches that's bleaching away from the bottom up

 

On my hydnophora the flesh is flaking off on the birds nest I haven't seen any flake off so it's just bleaching I guess