Hi Natalie-
Are you mincing the garlic yourself? It is the allicin being released when you cut or crush the clove that is what kills the parasites. I would cut it and let it sit for about five or 10 minutes b4 adding it to their food. If you buy it minced, it might not be as effective. It sounds like you are being careful with it. That’s good. I along with many others on this site have not had an issue with it.
Also, in all my research, I’ve never come across Vit C being used to rid the parasite and agree with anon that adding excess vitamins to an already balanced diet is not a good idea unless directed by your vet.
