Well, it sounds like the general vet is only putting a band aid treatment on a possibly serious issue. True, the physical inspection of the extent of the tail rot is the first stage, but real bloodwork needs to be done to isolate the offending bacteria and funguses present. Peroxide and Lamisil seems to be putting a band aid on the condition. I would think the general vet should've given a referral to a "herp" vet for follow up. The bacterial and fungal pathogens really need to be identified microscopically and through appropriate testing to eradicate the illness. The tail is a very important structure in reptiles.