What brand UVB are using?
You should try and bump the basking temp a little higher (somewhere between 105 and 120) and the cool side during the day should be around 85. During the night it is OK for the tank to drop to 60. Mealies are not the best for bearded dragons as there shell is very hard for them to digest, you should really stick with the crickets and maybe some silk worms.
Take a look here for some help with the foods you use:
http://www.beautifuldragons.503xtreme.com/Nutrition.htmlAll dragons (even more important with babies) need to have their protein (bugs) dusted with calcium at least 5 times a week and multivitamins at least 2 times a week. You will need to pick these up from a supplier or your pet store. Without the proper lighting and calcium your dragons runt he risk of developing MBD (metabolic Bone disease) which over time can become irreversible or lead to death.
Do you have the housed seperatly? If they are only 4 months old and not that big you may be able to just a piece of card baord in the tank to seperate them until you can get another VIV setup to properly house them. Just make sure they cannot see each other.