If you could only find a few mites visually, your case of them is not very bad ... The reptile spray will do a lot of good and could possibly remedy the problem without the PAM ... I also have been in the situation of not being able to have a separate room for quarentine ( we can only do the best our situation will allow)..... As long as you put the enclosure with your new snake on the other side of the room from the others and make sure you don't handle them after each other you should be ok with not having to worry about transmitting the mites to your other snakes, I would still recommend treating them with the reptile spray as well