I would agree with Prin on the food recommendations. I also feed a regular formula to my dogs as they age and don't bother with senior formulas. For overweight dogs I also feed a regular formula but in order to aid in weight loss will feed less.
My dogs eat Solid Gold supplemented with Seameal and Omega 3. I also add things like sardines on occasion. They all have beautiful coats.
It might be a good idea to have her tested for thyroid problems. It is a simple blood test.