Molly with red/white poo?

[mareeeeeah]

I have a 20 gallon tank with a group of mollies, two cory cats, and a mystery snail (cory & mister snail is new) anyways one of my younger mollies or the last day and a half or so had white poop with a red line just hanging off of him. he is hanging out right by the heater and in corners at the bottom. what is wrong? is it a parasite or something?

 

[Placroix29]

Do you feed your snails or catfish wafers? Or cucumber or zucchini? Bc it could be that if you do. I have a place that loves cucumber slices.. But my mollies will pick it and there poo turn white from that