"Easy" corals dying, difficult corals thriving

I know I haven't been on much lately - life has gotten in the way - but I know you guys are always the best when it comes to problem solving. Over the last few months I've been having increasing trouble with some of my oldest corals and the ones that should be fairly easy to care for. Over the last month a few have really gone down hill and likely won't make it if I don't figure out what is wrong very soon.

Corals that are struggling:

* green/orange birdsnest colony - one of my oldest corals that had been thriving for a year and a half - now is browning, starting at the tips, and polyps look terrible

* Monticaps (purple and red/orange) - losing color and have a dusty appearance to them, but nothing blows off. I've looked up some of the white-band diseases and it doesn't appear to be that

* trumpet coral - tissue loss, browning, not very fluffy anymore - this is another one of my first corals that has really thrived in my tank up to now

* zooanthids - yes, we all know these guys are tempermental and I'm not sure this is really related to whatever else is going on, but sadly I've continued to lose many of my zoa colonies

* plate corals - I have two home grown plates that are now receeding and unhappy (were happy for almost a year)

* hairy mushrooms - color loss and shriveling - have now split into several tiny corals but never grow or re-extend before splitting again. I kind of feel like they are splitting to save themselves rather than because they are happy. My clowns host in these and up until a few months ago they were happy. It started as a single very large mushroom (probably 8-10" in diameter when extended), and now is several smaller ones that don't extend more than 1-2".

* chalices - some have died some are okay

Corals that are thriving:

* all of my acros - tricolor, red planet, bonsai, larry jackson, pink lemonade, tortusas, strawberry fields, red/pink birdsnest -- this is despite seeing red bugs in my system

* orange digitata

* australomussa

* acans

Corals that seem completely unaffected

* frogspawns

* torches

* pearl bubble

* meat coral

* leather coral


Other system info - my fish list is accurate. I've wondered if some of the trouble could be related to my watchman dumping sand on my bottom corals, perching on the trumpet (newer / more frequent behavior recently), and the melanarus flipping over the plates while hunting critters. Water changes have gone down hill a bit with life being nutty at the moment, but I did do a large water change before going away on vacation and things only look worse now that I'm back. Nitrates are minimal, and dosing schedule hasn't changed. I also have to say that I think I'd see problems with the acros before anything else if this was a nutrient issue. I also don't have algae issues other than bubble algae. And no recent changes to my lighting.

So, any ideas as to what would be taking out my birdsnest, monticaps, and trumpet but not affecting other lps or acros?

 

It sounds like a doc issue. Have you checked your mag/cal levels lately? I would start with more frequent w/c's and see where that takes you

 

can you post some pics and your water params (cal / alk / mag / salinity)

sound like it may be different issues.

are your montiporas losing tissue (i.e. you see patches of white) - if so may be nudibranches

plate corals - may be a flow/lighting issue - try moving it to a different spot in the tank. you should feed them once in a while.