I found a ziploc bag in my cabinet and put some fish inside. Afterwards, I noticed that there were some flakes in the bag. (The bag wasn’t in its original packaging. I guess someone used it and then put it in the cabinet). Some of the flakes/shmutz got on the fish that was for shabbos. Is this a kashrus problem that I should be concerned about? I have no reason to assume that the flakes were milchig (or not food).
If you are sure that it isn’t an insect, and it isn’t milchig, then it should be alright.
Have a good Shabbos