LPS corals receding

[gmann]

so ive noticed that a couple of my scolies have started to recede (some more than others) and pretty much all my euphyllia are now dead. i have increased gyre output from 40% to about 50-60% to combat algea, which i assume is why my euphyllia are now done, but i dont get why the scolies are dying.

Here are my paramters. I have noticed that they have risen since i switched from AF reef salt to Salinity.

Salinity: 37ppt
Cal: 440 - salifert
KH: 8.8 - salifert
nitrate:0 - api
phos: 0.04 - hanna
water changes: every 4 weeks, about 60 gallons (25%) using Canadian Springs bottles

based on web searches, all seem to be fine except my phos, but even when i had a phos reading of 0, i still had algea issues, so im not quite sure what im to do anymore.

i've been dosing phosdown every 2 days to combat the algea issue. zeobak 12 drops every wed & sat, and upped my skimmer to fill up every 2-3 days. I don't dose any alk or ca and my parameters stay steady. Feeding has been cut back to once per day.

Is there somthing i am missing or not doing that is causing this?