I need some help, on behalf of my lab mix and my rough collie.

Here's a little bit of background:
Tucker is a 4 year old floppy-eared lab mix, we adopted him 3 years ago. For the past year or so, his ears have been bothering him alot. A few times, it has been an ear infection. Other times, he rubs his ears, but doesn't have the same smell or discharge. My collie is almost constantly trying to lick inside his ears, which she didn't used to do, so there is obviously something going on. No food change around when this started, though he only had one ear infection when we lived in Louisiana (yeast) and his frequent problems started since we moved to Georgia. I'm thinking either an environment allergy - something that wasn't in Louisiana. Or maybe a food allergy that is just getting progressively worse (he has always licked his feet).

Colleen is a three to four year old rough collie. We adopted her two and a half years ago. She was found nearly naked and bloody, due to a severe case of demodectic mange. Mange returned due to the stress of moving to a new home (ours), but mite population has been relatively normal since that incident when we first brought her home. Groomers in Louisiana commented that she had dry skin. We've got her on a wild salmon oil supplement that gets added to her food daily. We moved to Georgia in fall of 2007. Late last spring/early last summer, when brushing her, we discovered that she never blew her winter coat. We literally filled a trash bin with all of her undercoat. Needless to say, I've been much better about keeping her brushed since. Damage was done, however, and she has had constant skin problems since. Not only did she have all that undercoat when it was too warm for it, but we no longer have central air so she only gets air conditioning when we're home. Not surprising that she wound up with a pretty bad skin infection. What I don't understand is why her skin has NEVER completely healed from it and the fur has never completely grown back. It's almost spring again, and she still has hair loss in the same places at the rear part of her back. Not as bad, but it's still there. She's been on numerous rounds of antibiotics and antihistimines. She doesn't scratch at it, but she loves to be rubbed there. Even during the winter, she had problems with her skin. Even shaved like a smooth collie, she has problems. Potential food allergy or environmental allergy? Funny thing is, at the dog park, everyone says how pretty her coat is. She looks beautiful. Until you push back the hair that covers her couple of thin patches and show people that she has some type of skin problem.

Now the history of their food.
In Louisiana, we had them on Beneful, but switched to ProPlan Sensitive Stomach and Skin when the groomer said Colleen had dry skin.
Here in Atlanta, we kept them on that until I got laid off (late September). Then I switched them to regular ProPlan to save money. Then back to Beneful Healthy Harvest. Though they've been on Purina One for a week because I went to 4 different stores and couldn't find a large bag of the Beneful. It wasn't until this winter that we took them off ProPlan, so both Colleen and Tucker's problems started before the switch - while they were still on ProPlan Sensitive Stomach and Skin.

I was looking at the ingredient listing for the ProPlan, and I can't for the life of me figure out what it is that they may be allergic to, so that I know what to avoid.Here's the ingredient listing. No corn. No wheat. No soy. The top allergens aren't there.

Salmon, brewers rice, canola meal, oat meal, fish meal (natural source of glucosamine), animal fat preserved with mixed-tocopherols (form of Vitamin E), salmon meal (natural source of glucosamine), pearled barley, brewers dried yeast, animal digest, salt, potassium chloride, Vitamin E supplement, choline chloride, zinc sulfate, ferrous sulfate, L-ascorbyl-2-polyphosphate (source of Vitamin C), manganese sulfate, niacin, calcium carbonate, Vitamin A supplement, calcium pantothenate, thiamine mononitrate, copper sulfate, riboflavin supplement, Vitamin B-12 supplement, pyridoxine hydrochloride, garlic oil, folic acid, Vitamin D-3 supplement, calcium iodate, biotin, menadione sodium bisulfite complex (source of Vitamin K activity), sodium selenite.

Anything on the list jump out at you as an allergen? Is it possible to be allergic to salmon or rice? (Keep in mind that even when on the lamb & rice pro plan, Colleen still got her salmon oil supplement.) If anything jumps out at anyone as a potential allergen, I'll check the ingredients for the other foods to see if it's also in those.

I'm not sure what to do for Colleen. It doesn't seem to bother her, but I feel like a bad dog mom because her fur hasn't grown all the way in and her skin is still flaky. I've given up on taking her to the vet. The medicine doesn't solve the problem, it just costs me tons of money to take her in. If she's still having this problem when I find another job, I'm going to ask her vet to give me a referral to one of the local allergy/dermatology specialists so that I can get their opinion.