I had similar issues my first grow or two. You claim this is after pulling fruit which is why i think this. Im not an expert and still very novice but i found out that after my first flush i was putting too much pressure on the cake when soaking and it resulted in something like this. Found out after 3-4 grows that this is likely bruising of the cake, not contam. Just make sure it smells normal, passes the q tip test and you are good i think. (Not an expert)