Clownfish - red blushing color?

[MilesHug]

Anyone know what this redness is from? Been trying to figure this out for a month. They act/eat/look normal otherwise. Can't see it with the blue lights on but best when the lights are off and seems to progress the longer they are in the dark.

 

[snorvich]

You should not attempt clowns in a 5 gallon tank.

 

[MilesHug]

It's a 25 gallon. I had an outdated profile (fixed now). Any thoughts? No flashing or clamping. Still social and eat well. The larger one has labored breathing. They have been like this for about a month. My LFS suggested to attempt feeding them Dr. G's antibacterial and antiparasitic caviar before/unless I determined the cause. Ammonia 0, nitrate/nitrite 0, pH 7.75 but seems to fluctuate a little, salinity 1.025.