Puppy multivitamins?

I shelled out $40 for a tiny bag of premium dog food yet he’s eating dirt and chicken shit like crazy, as if somethings missing. He doesn’t eat his dog food much but will chow down on cousin’s dog’s crappy Pedigree food.

What gives? Why would he be missing anything if his food is such high quality?

He feels very warm tonight after eating mud that was dug out from 2 feet deep. Will take him to vet tomorrow if he’s not himself.

He’s a farm puppy (5 months) so no we can’t really keep him away from things, no one has time to keep an eye on him with all the work needed to be done.

Any tips? It’s driving me nuts watching him run away with chunks of dirt!