Ear problems

Well both dogs are having issues with there ears.  I noticed yesterday evening that Sadie's ears are really red with some very small scabs which are a result of scratching I guess.  Charlie had a spot on his ear that was a scab, well Sadie licked it off and there's a big red bump there.  I'm guessing Sadie has gotten ear mites, only thing I can think of with Charlie is possibly a tick bite.  We give them Frontline regularly up until the first couple of frosts.   Anybody got any ideas on what could look like a bubble that's red on Charlie's ear?  This is on right at the side, not really in the ear canal itself.  Sadie's ears are red down in the canal itself.