Vet visit: yeast infection in ears

Raven (13 weeks) went to the vet for shots.

The vet swabbed out his ears and there was all sorts of brown gunk - even on the 2nd swabbing. Vet looked under a microscope and there were no mites so he gave me medication for a yeast infection and some ear cleaner to use after the medicine.

His ears were not red or hurting but he had been scratching - he scratched when he arrived at 8 weeks and I thought it was his collar annoying him, but he has kept it up (sitting and scratching periodically but not obsessively) A month ago at his last shots (with a different vet since this one was on leave) the vet said his ears were okay.

The vet was really surprised to see see such gunky ears in such a young pup.

I know that food is implicated in recurrent ear infections, but from what I could google it takes a while for food allergies to appear, so I don't think I'll switch his food yet until I see if this clears up or if it re-occurs. (He's eating Nutro large breed puppy - there aren't a lot of choices here in town. The vet is really into Science Diet/Hills but I don't like those - the large breed puppy has corn as the 1st ingredient!)

I guess I will be hyper-vigilant about cleaning his ears - luckily since it wasn't painful yet he didn't mind at all getting the medicine and his ears massaged.

He also weighs 31.8 lbs. And he's pretty lean (IMHO) - he's leaner then at 9 weeks when he weighed 20.4 lbs) According to the lab growth chart, he should be at 27-38% of his adult weight and will weigh between 83 and 117 lbs as an adult. Hope its at the lower end of the range! His Dad weighs about 90 lbs.