long tentacle plate coral issues

[Qasimja]

do any of you have problems keeping long tentacle plate corals? ive had 2 over the past 3 months die on me the first one i thought one of my clowns irritated it to death cause it was tryin to host it so then my other one melted away too i just recently started dosing my parameters are below they start out fine then after a while the polyps stop coming out so much then it starts to melt i did have high nitrates and phosphates at one point nitrate was 40 phos was .5 could that have killed them? i will check those again today or tomorrow all the rest of my corals are doing great and growing

alk was 7.7 i moved it to 8.6 and its holding steady
calc 450
mag 1350
temp 77

 

[Daddy-o]

Ours dont seem to like really high nutrients. On a side note, my son fragged ours and I had a frag glued to the rockwork. About a month later I removed it and now there are 15 or so babies growing on that spot on the rock.
Cheers! Mark