RBTA behaving weird

[A.Percula]

Hi,

I noticed my RBTA is behaving weird. I introduced her to my tank a week ago and din't move for 5 days. Last 2 days she started to move but still in the same rock. I decided to do a 15% WC and I noticed a brown smoke coming our of her mouth (see pics). It was not a string zooxanthellae coming out, it was more like "smoke".

Water parameters:
Salinity: 1026
pH: 8.0
Kh: 10-11
Nitrates: 0.20

Any thoughts?

 

[amazongb]

Need more info.. lights, how old is the tank?

 

[A.Percula]

Tank is not that old (3 months), but I've been monitoring water parameters and they remain very constant (the ones I can measure Ammonia, Nitrites, Nitrates, Phosphate, KH, Calcium). I have an ATO to keep salinity on point at 1026, pH is always 8.0. I've a skimmer and temp is always 78. I used water and rock from a friend's tank so my cycle was short. The only "major" change was lowering nitrates from 10 to .20, so she was probably happier with a bit more nitrates. For WC I use RODI water matching salinity and temp.

In terms of lightning, I do have an Al Prime HD LED. She came from a tank that had less light, so I lowered my intensity a bit.

All my fish are on a separate tank going thru treatment.