The reason they have Metabolic Bone Disease is because you don't a
UVB light. The "Intense Basking Spot" bulb is a heat lamp ONLY. I highly suggest reading this over:
https://www.beardeddragon.org/articles/newbies-guide-lighting-help/
Bearded Dragons need two lights, one heat and one UVB. SOME bulbs (Mercury Vapor Bulbs) produce both but your light is only a heat lamp, so it produces no UVB. UVB mimics radiation from the sun and allows dragons to make D3, which they need to absorb their calcium. Without UVB, you can feed them as much calcium as you want and their bodies won't absorb it, which is what happened here. UVB lights should be long strip lights like:
http://www.lightyourreptiles.com/24-ho-t5-double-bulb-fixture-with-arcadia-12-and-6-5k-day-light-bulbs-included/
These bulbs need to be replaced approximately every year as UVB output goes down. Even if the bulb is still working, it may not be producing UVB.
Do you have any way to measure temperatures? You'll want a thermometer with a probe or an infrared temperature gun to make sure their basking spots and tanks are indeed the correct temperature.
<<<< these are very good, I've tested them and found they are accurate within 1oCelsius.
http://www.ebay.com.au/itm/4x-LCD-Digital-Temperature-Thermometer-Fridge-Freezer-Aquarium-Fish-Tank-Reptile-/391259141696?hash=item5b18dcb640:g
Just curious, what substrate do you use? Meaning, what is on the bottom of your tank? Do they have problems pooping? It would be best to fix the reason they have problems instead of giving medication if not necessary.
