Honestly I don’t understand enough of the backend to tell what’s going on, but from what I understand some instances can have trouble with backlog from especially large instances (like lemmy.world) that can make federation slower, it might be related to that? I don’t think Blahaj is particularly large comparatively, but having to spend more time federating with huge instances might still affect how quickly things federate.
I don't either. My main is on lemm.ee and blahaj.zone has just been gone for a week. But this is why I have accounts on any instance I actually care about, there's so much that can and does go wrong.