Banggai Cardinal Strange Behavior

[CVAquarium]

Hi all, I bought 3 banggai cardinals a couple of weeks ago and they all seemed fine up until today. Tested parameters including temp and salinity and all looks good.

One banggai died earlier today, and now a second is by the surface of the water breathing a bit heavily. I attached a video for reference but any help would be much appreciated.

 

[ReefED!]

Could be velvet

Might also not be that

I had 2 cardinals for over a year and they grew to be full sized and one died rather suddenly in a similar fashion

Wasn’t velvet