I feel like a terrible puppy parent

I have a 10 week old Dutch shepherd mix and I feel as though I am doing him wrong. I watch him 24/7, crate training, being careful with him being outside and the other dog but they’ve both been diagnosed with Giardia and one with coccidia. Despite my constant vigilance I am afraid that I have failed him and my older dog and I don’t know what to do. A side effect of their medication is lack of appetite but now my baby won’t eat or he’ll eat very little and it’s one of the only ways he’ll take the medicine. It makes me so upset and anxious, he’s my first puppy I’m raising completely on my own and I just want to make sure he’s gonna be alright