Is this what the vet gave you? http://www.amazon.com/DeFlea-Reptile...=reptile+spray
If so spraying weekly may be to often. I don't remember but if it is what you got follow the directions. Also it is available online and at both big box pet stores.
I had mites once which came with three snakes I ordered online. I used the above spray and got rid of them with one treatment. I sprayed everything including the carpet around the snakes and then vacuumed.