You should be virus testing this one also. it sounds as if they picked up something from the “guy’s” facility and not necessarily parasites. Unfortunately virus are not susceptible to antibiotics. The majority of captive born ball pythons aren’t going to have parasites unless exposed to wild caught bps or prey (not that it couldn’t happen). You can also take a stool sample to the vet to test for parasites.
Im going to call tomorrow and see if i cam get one ran. Our local vet that will see snakea is a real jack ass. They charge my the second. Ill call though…
Have you noticed any greenish or bluish mucus in the diarrhea?
The soaking may have been a response to dehydration, not necessarily related to cause - more so effect.
You need a vet for the diagnosis, were I in your position I would strongly suggest to the vet that this could be amoebic dysentery/amebiasis. You have to be diplomatic in communicating this; make them think it’s their idea.
Agree with all assessments that you need to get some tests done to ID the issue rather than just blindly shooting around with drugs. Fecal exam, bacterial type and sensitivity, and possibly viral (I would specifically check for adenovirus but paramyxovirus and serpentovirus are not bad to look for as well)