Help

Try metro flakes - or if you want try soaking their food in epsom salt. But ultimately is sounds like your fish has a parasite in its stomach which is very common but not always the easiest to cure but not impossible by any means.

The second thing is apistos don't have long life's especially albino's.

I was lazy and ordered some NLS Hex Shield that I give when ever I get wild fish in or fish with sunken stomachs.

Are you adding salt to the water ? You may want to put him into a tank by himself .. He may have a parasite . Continue to do regular water changes to the main tank and add salt ..