Carpet anemone not doing well

[syncro]

Despite my best efforts, this green carpet anemone is not doing well. It is not fully expanding and patches of tentacles are not opening. Mouth is occasionally gaping but is not expelling its insides. It is occasionally spewing slimey balls like it has eaten though I have not fed it in a week. After purchase (from a fellow canreefer) it did great. It was eating, sticky and fully expanded a few days after introduction. Three weeks in, a failure kept the MH lights off for 2 days and the salinity dropped to 29ppt. I corrected the both but since it has been declining.

Three weeks ago:


Now:



Tank: 40G, 8 months old
Lighting: 250W MH on 8hrs/day, 4 x T5s on 10hrs/day
Temp: 24.3 - 24.6*C
Salinity: 32ppt w/ ATO
Ammonia: 0, nitrite: 0, nitrate: 0, pH: 8.4
Filtration: Skimmer, 3.5" DSB, live rock, carbon
Livestock: carpet, RBTA, GSP, occelaris clownfish (everything else moved to the sump)
Livestock in the sump: porcelain and hermit craps, sexy shrimp, cheato
Maintenance: Weekly 12% water changes with RO/DI water mixed for at least 24 hours
Feeding: mix of frozen shrimp, scallop, squid and krill chopped fine

I've ruled out (to the best of my knowledge)
- stability - controller keeps temp and salinity rock solid
- lighting - carpet closes up when light is reduced or partially shaded
- irritation - I've moved the crabs and shrimp to the sump, nothing is touching the carpet
- stray current - tested and found none

Possibilities
- chemical warefare with RBTA - I am running about twice the recommended dosage of carbon in high flow area. RBTA is showing signs of stress.
- disease - animal was sick and got infected in my tank and took several weeks to show it
- water quality - I experimented with heavier feedings (few grams every other day) so perhaps tank is having a hard time keeping up though the ammonia/nitrite/nitrate tests all show 0.

Any suggestions? I don't want to see this animal die. I am considering giving it up if it doesn't turn around very soon.