I wouldn't use a spray anymore. That can do really bad things to a rats respiratory and that is formulated for a snake not a rat ): Only things that are approved for a rat is revolution.
Since if it is mites, you will need to dose the rat again in a couple of weeks. It could kill your rat to use that spray so I wouldn't do it anymore. And who is to say if it actually works for rats ): I would order a thing right now, and treat both rats as if one has it the other probably does.
If you are so reluctant to ask or go to a vet, and many would sell you some even without an appointment, you can order it at petshed:
http://www.petshed.com/products/item107.asp
I too am dealing with mites ): It's not fun. That's what the vet prescribed for me. He told me to give two drops on my 500+ gram boys and just one on my wimpy little 300 gram hairless. One vial treated them all. He told me to give them more in a couple of weeks.
My advice: don't do any more treatments with that spray stuff. Order the revolution, wait for that to come in. Treat both rats with two drops. Clean EVERYTHING freeze wooden toys and vacuum or mop around the room they are in.