Crumbliness is usually from excess moisture retention/ph gradients after the point of curd fuse. What happens is that you have large or uneven curds for the cheese type, then they keep excess lactose, and meso bacteria keep eating the lactose and producing lactic acid, even after brining. The fix is not so much about ripening time pre rennet, as it is focusing on drain pH, even curd size, and pH at brine. So yes, it is excessive acidification, but the acid is created after gelation. While milk is in the liquid state, the acid is distributed evenly, and won't really result in too much crumbliness... unless you're waiting many hours before adding rennet.
Washing does help. Garrotxa has a 10-15% wash usually. Good luck. Hope they turn out well.