i am no expert but there have been alot of people saying lately that frontline isnt working on the fleas anymore as they have become immune to it!! so that might be why your cats still had them despite being treated.

i have also been told bob martin stuff is rubbish and potentially harmful to your cat. again i cant remember the specifics but i am sure there are other people that can tell you or you might be able to search for the threads.

personally i use advocate. this is a spot on i got from my vets. it treats fleas and most worms. i was told to use this monthly and then about twice a year giving them a full wormer.

hth