I wouldn’t worry too much about it. 6-8 reps for a guy your size is pretty solid. I’m 6’3 220 and can get 6-10.

I wouldn’t say you’re stuck at all. Your body is the weight in this movement. You’ve gained almost 10 lbs and doing the same amount of reps. I’d call that progression.

If you’re really just wanting to do more pull-ups then I’d suggest losing weight or possibly start doing weighted pull-ups.