How long has it been runny? Sometimes they just get upset stomachs and it resolves on its own. It can be caused by something in the diet or dietary changes as well so not necessarily a problem. If it continues to be runny for several weeks it may be worth having a sample checked by a vet for parasites though.
I just set Swordtail's timer for his bath and paused it so I could actually fill his soaking bowl up and he crawled over my phone and canceled the timer
Mirage came out of brumation on April 26. He was doing great. On May 2 he started acting funny. We just redid his tank, and he keeps going into one of his hides. He just lays there. He shows no intrest in food. HELP!