Given the size of the tank and the fact that you have an imcomplete school of tiger barbs (who are aggressive toward other fish when not kept in proper schools of six or more...more being the better end of that deal), I would say your platy is probably stressed. I would remove the tiger barbs and ladder loaches, and depending on what kind of catfish you have (I love that people don't realize just how vague calling your fish a "catfish" can be...no offense, just a random observation), remove it as well.