Xterms:
Actually this is not unheard of. I've observed this in pet birds that during bath time when they are in a heightened state drink way too much and get really runny poo. I have observed animals (horses, cats, birds) getting bored and becomes obsessed over something like playing with their water or overeating when they are bored or stressed. Usually with cats they puke water. Horses I'm not sure. Mine have been more interested in splashing it than drinking it. I'm not sure if that's applicable to chins specifically.
Even the most meticulously designed systems can't account for all possible contingencies. Some animals can be prone to self-destructive behavior because of genetic defects as well.
I have read several case studies of giardia outbreaks in chins and this seems to be more consistent with diarrhea under stress for chins. However like Jamie said in her last post, Toki will need to better define diarrhea, which in my mind is different from squishy poo. So Toki please let us know.
I hope it's not because antibiotics are notorious for causing chins to stop eating and owners to have to hand/syringe feed in some cases and must carefully regulate their diet and water consumption through the course of the antibiotics. But, if it is a giardia infection and it's not treated there's a possibility it can destroy the intestines and cause them to bind up and cause serious complications like rectal prolapse, malnutrition, and death. It's just not a pleasant experience for anyone to have to go through so I wanted to throw out simple things as a possibility to rule that out and see what others might say. True liquid diarrhea is always a danger sign in chinchillas and rodents though and should be diagnosed.