Pics would definitely help. There is a problem on the forum so you either have to upload pics from a mobile device or via photobucket.

You should be dusting with calcium every other feeding and multivitamins once a week.

Vitamin d3 is just as important for bone health as calcium. Without vitamin d3 your frog won't do very well.

I'm not sure if it is curable. I had a frog that died from MBD about three years ago. But even if it isnt curable, it will not continue to progress if you begin providing proper supplementation.

As for why they eat less, i have no clue. Hopefully someone with more experience will chime in