Grrr. My post got deleted so if it shows up magically, I apologize for a repeated post.
Keep trying different kinds of hays. There’s quite a few on the BB store, all acceptable for extended use. The oat hay is what got my rabbits to eat hay. You can either order off of here, or see if you can get some of the same kinds locally. Depending on where you live, the farm and garden section of craigslist can be a good resource. I can get all sorts of hay where I am!
You could also try a hay topper like this: http://store.binkybunny.com/bunny-bouquet-hay-topper-p118.aspx
In addition to providing other kinds of hay, you can “cut down” on the pellets you feed them. You don’t necessarily need to lessen the amount given, but you could just provide pellets in the morning and evening, rather than keeping pellets out all day long. This will encourage them to eat more hay when they are hungry, as they can’t bank on eating pellets through out the day. 