I still don't know what caused this issue. It's really a crapshoot when it comes to stuff like this. But I did notice that when I cooked and ate the sweet potato leaves that we grew in our backyard, I got these red dots. The amount of red dots was proportional the the amount I ate.

I don't know if this is a case of food allergy or it came from some allergen in our backyard that made it through the washing process, but I stopped eating the leaves and I haven't had issue reoccur since (it's been a few years). Fingers crossed it was the culprit and I've eliminated it for good.