Well Blue Buffalo isn't a grain free food unless you're feeding the Wilderness version. But I would put a call into the company to make sure it is an all life stages food as it looks to be geared more towards adult dogs.
Wow I cannot believe that they gave her vaccinations when she has mange! Shame on them! I would also consider finding another vet if that is the case because that's absolutely awful. Just make sure to hold off on spaying until 2-3 months after the mange has cleared up. The dip is very toxic, many end up with diarrhea, vomiting, lethargy, stop eating, and some have died so I'd definitely skip that. You can do research online on it as well.
On vitamins, ones that are good that don't break the bank are Canine Plus vitamins. I get mine online at
Amazon.com: Online Shopping for Electronics, Apparel, Computers, Books, DVDs & more and get the big tub at a decent price.
I'd also highly encourage apple cider vinegar, 1 TBSP a day mixed in her food should be fine (1 1/2 tsp twice a day would probably be best). Make sure it's the stuff you get at a health food store or in the health food aisle that says organic with "the mother" it isn't the stuff you use for salad dressing. It's GREAT stuff and really helps build the immune system and it's cheap ($5 a bottle or so). I get mine at my local grocery store in the health food aisle but you can also get it online or at places like GNC or any other Health food/Health supplement type of store. Bragg's is the most common brand.