Chin contantly eating poop

[jennmessenger]

I know it's normal for chins to eat their own poop, but one of mine has been eating every poop. We've been treating him with probiotics, cisapride, belly massages, and exercise, but I can't seem to get him back to 100%. Now our other chin has started to excessively eat her poops.
Is this a sign of a viral or bacterial infection?

Thanks