How can I treat my hamster's wet tail?

So.. my teddy bear hamster has wet tail. I’m 99% sure he does actually. I read up on it and have had hamsters with it before but I treated them by washing it away and got results. Also it is most common in teddy bear hamsters. Teddy bear hamsters 3 months old get stressed being away from their mum and siblings and soon get it after seperation. I’ve had him a week today and Petco (the place I recieved him from) says they’ll treat him, but the catch is I have to return him for them to give him treatment and after treatment I have to buy him back, but if someone before me plans to buy him then he’s not mine anymore.. which is weird. PetSmart said that if I keep him clean and leave him alone he’ll heal on his own since wet tail is do to stress. This contradicts my knowledge on wet tail because it says with symptoms showing I need to take him to a vet immediately for treatment. It’s hard because here seeing a hamster just to tell me he has wet tail is 32–50 dollars PLUS treatment.. what should I do? Should I continue to clean him and hope for the best? Should I return him and risk not getting him back? Should I just buy the treatment and treat him myself?