It may be that it's not massively deficient and has taken a long time to get noticeable, or it could be a magnesium, phosphate, or Vitamin D deficiency as well. They work together.
I would guess it's a vitamin D issue, because most rabbit pellets don't emphasis that.
The first supplement I can think of is Ryerson's, I know it has clovite in it, which is a vitamin D supplement. Maybe some other people will bounce in with some others. I first considered suggesting Calf Manna, but again I didn't find any nutritional information for it's Vit D.
You could also make your own supplement. If you would like help with that let me know and I'd be glad to offer some suggestions. I know there have been some magazines, I believe Empress that have had some supplement recipes as well.
ETA: Volunteer Chin, if the whole herd is deficient, it's probably something that needs to be addressed with the feeding program. If the teeth are losing color, then they're low on calcium, which means the bones are too, calcium also regulates things like heart rate in the body, it's a very important mineral.