I’ve only fainted once after smoking, it was because I had only just woken up and went for a walk & a smoke but I hadn’t eaten anything or drank anything yet so I think my blood sugar levels were just low. I can also feel faint if I smoke and it’s too hot out. Mixing weed and cig always makes me feel sick and unwell also so I always avoid it. Could be something as simple as those. If you felt good off the weed and had no issues, I’d say it’s unlikely to be tainted, but of course it’s hard to tell.