Grass won't spread (or does but extremely slowly)

Grass isn't spreading from a covered block to a regular dirt block. I've been in the proximity during the daylight and it's been an (in-game) week and there's no difference, still.

It's really a problem when you're doing landscaping, or especially when you've got sheep rotating around in different pens, but the original pen's grass still hasn't grown back yet so now you've 4 grass-less pens and a bunch of naked sheep.

I also had some coarse dirt blocks strangely turn into grass-covered dirt blocks immediately after the newest update, though that's kind of a different matter altogether...