Parasites are a possibility for loose stool but it could be nothing or it could be more serious. I would make sure the humidity is correct and that there is water, always. Keep a close eye on it, any sign of change go back to the vet. If you have a good relationship with your vet it might be worth a phone call so she/he knows what is up and what you are doing. I would make sure to weigh the animal as well and keep a close tab on weights. It could even be worth if you feed F/T to use a small syringe and add a little (1ml or two) of filtered water to the rat. I just poke it down the maw of the thawed rat and feed to a dehydrated snake. I guess make sure the snake does not become dehydrated.