I'm sorry to hear your little guys are having trouble. I have had the same problem with poor tongue extension. I have had many chameleons and never had that problem until I hatched out many babies at once. Periodically I would get one with poor tongue extension at different stages of their development. I came up with every possible theory I could think of but none panned out so I went back to the basics. i called Linda Davidson( i would highly recommend her book) Linda convinced me it was lack of calcium and suggested I powder their prey with calcium(I am a big fan of her product miner-all but rep cal with d is sufficient)EVERY DAY until subadulthood then weaning back was o.k.Her product is designed to pass through the cham if not utilized by the cham. Sure enough, I never had the tongue problem again. Now as far as why it would come up periodically I noticed it was after separating the chams into more cages as they got bigger. My guess is as they would no longer have as much competition for food and have a growth spurt but calcium needs for that growth spurt were not being met. Im glad someone mentioned those uvb coil lights. I cant believe they even made it onto the market because they will and do burn the retina of your lizards eyes! Good luck with your little guys.