Banghai Cardinal with large eye

[SaltieG]

I purchased two of these cardinals 3 days ago and right now they are in the QT. Anyways I came home from work tonight and see that one of them was in the corner hiding and one of his eyes has ballooned up very large. His other eye looks like it may be starting to do the same and he is breathing rather heavy. The other one seems to look normal. Any ideas what could cause this? All parameters of the water are just fine.

 

[krowleey]

maracyn two for saltwater fish, dose a double dose for the first day and cross your fingers.

 

[SaltieG]

I already have copper and prazipro in QT, will maracyn be alright to add? Also, what could be the actual cause for the eye problem that the maracyn treats?