need help with female BD - heavy breathing

[Squid]

Need help, yesterday, i noticed my Female BD suddenly seem to be breathing heavier than usual, also when i dropped food it just ignored the food and not really active?
usually it will immediately go for the food i drop. not sure what is the problem with her.

I tested water for Ph and Ammonia
PH - 7.5
Ammonia - 0
tank size is 350 Gallon, with 180 gallon sump.
tankmate is a 24 inch super red arowana and a big King kong parrot which dont seem to bother my rays.

I did a 30% water change and dosed with Prime, not sure what else to do.
She is about 12 inches now and with another male BD.

before this i think i saw her covering the male BD or is it the other way around, not really sure.

what else can i do?
earlier today she seems more active, but still seem to be breathing heavier? and doing chinups, where her front chin seem to be blowing?


is it possible she might have been stung by the other ray?
or maybe she ate something which should not be eaten?

no new thing introduced to their tank.