I'm afraid that a vet may be your only option and NO! This is not normal behavior. Whoever told you that seizures are normal is down right idiotic and obviously knows nothing. That's like saying that its normal for anyone or any animal to have seizures.While common in some dog breeds it is still not normal. I wouldn't take it to them for anything.

You do need to take your White's to a vet that specializes in amphibians. You aren't the failure. If you are doing everything right and trying your best. Sometimes these things happen. I know its frustrating. Just gry and stay calm and get help for you frog. The problem could be neurological. Or caused by some sort of dificiency.