Very unhappy RBTA- Help

[ahl]

Bought this RBTA a few months ago. It was doing wonderful until one day it started to feel unhappy, its mouth started to show and lose body mass. When flow is off it totally cannot hold itself up.
There is another small one in the same tank doing well. The tank went in fallow right after I brought her in.
Should I treat her w/ cipro?

 

[link81]

tank parameters?

 

[ahl]

No3 - 10
PO4 - 0.5
Alk - 7.7
Mg - 1320
Ca - 390

API tests

 

[link81]

anything change?
temp, lights, flow, salinity?

 

[ahl]

Nope. Very stable lately.