What I meant is there could be some change to the share difficulty at nanopool. I didn't mean the ETH network difficulty, that one obviously changes all the time. Share difficulty is the minimum diff limit that each pool sets for shares coming from the users (nothing below that limit gets accepted). Most pools use var diff, but Nanopool uses static diff. Right now it's 5 billion. Could've been lower 2 weeks ago, I don't know. If it was lower back then, that would've explained why you've had more shares accepted before. But that's just a guess, I've no idea whether they changed that during these 2 weeks.