need help, keep losing coral

[bonomo53]

So my tank was doing great, till about june when i started losing coral. I lost some sps colonies to rtn, lost a few chalices and now my acans and sps colonies are slowly receding from the base up. I cant figure out what the problem is my params are all in check. I dose cal and alk every night and have been doing this for around 9 months now and haven't had a problem until this so don't think it can be an alk swing. I haven't lost any fish just coral. Only thing i can think of is that my t5s haven't been changed in about 11 months. But don't think that has anything to do with it.

Alk 9.6 Dkh
cal 450
mag 1430
ph 7.9-8.1
phos .25
salinity 1.027
nitrates 0
ammonia 0

[bertoni]

That phosphate level is very high, if accurate. I might add some GFO to the system. If a LFS can run a phosphate test for you, a second opinion might be useful, though.

Activated carbon can be useful in some cases, too. Is there carbon in the system?

The other numbers are fine, but double-checking them is a reasonable step, if it's not too difficult.