Calcium + D3 is what you need to be dusting with. UVB is not necessary although there is nothing to suggest that there is anything wrong with adding it. Most monitor keepers don't use UVB since the diet of these monsters allows them to not need it at all and it has been proven time and time again. They won't double in weight monthly the entire first year as stated above but they certainly do grow like weeds when properly supported. In a year in captivity a male should be around 3 feet and a female should be a little over 2 feet.

Keep an eye on the ambient temps if the enclosure is in the garage during the summer since it can get pretty hot and if you have an exceptionally hot day it could be deadly.