clown distress

[Nano]

My female clown was just swimming around minding her own business happy blah blah... I fed the fish some nls flake, she ate then I went for supper. Come back and look, she's at the bottom breathing rapidly, and laying on the bottom...

Parameters are

Nitrate 0
nitrite 0
Ammonia 0? Slightly darker so I added some stability
Phos 0
Alk 9
Ca 420

Salinity 1.024

I don't get it, and I'm not sure what to do, everything else is fine, she's just really stressed/possibly dieing....
Also pointed a powerhead to the surface.

Only recent change was Saturday I removed half the LR from my tank that was taken over with gha so I'm cooking it. But there is still about 20lbs in the tank. Her colors normal, pattern looks good. Has one or 2 small black dots on her, but always has. I can't get a pic as she's at the back of the tank and I don't want to move her and stress her out, please help guys she's fading quick.