I'm very sorry he passed away, unfortunately it doesn't matter how much Calcium you feed a bearded dragon if you do not have an appropriate strength UVB tube and a bright white basking bulb right alongside each other, the UVB tube mounted under any mesh lid and withing the correct distance of the main basking spot, and the 3 major temperature zones withing the correct ranges. Without an adequate strength, long UVB tube that is mounted under the mesh lid and within the correct distance of the basking spote (usually within 8" unobstructed) they cannot manufacture any natural vitamin D3, which is what allows them to absorb Calcium. And without the correct temperatures, especially the correct basking temperature, they cannot digest the calcium or multivitamin powders, nor any food at all that they eat, so that also keeps them from absorbing and processing any calcium, and usually stunts their growth as well.
If you are planning on getting another bearded dragon, please just come back BEFORE you go get him, and we'll be more than happy to make sure you not only buy the correct UVB tube, basking bulb, and thermometer, but also that you have the UVB tube mounted correctly and the basking bulb and the temperature gradient set up correctly. That way this time you'll be ready to go and get your new little guy off to a good start...