Do you have a heat light now?
You should. Inadequate basking temp can cause the symptom you are describing. Babies should be able to reach at least 85 degrees (I go even higher, many on the forums do not without problems, but I would definately make sure you have a hot spot of some sort in the enclosure and not rely on ambient temp). It is important the babies be able to escape the heat when they want as well- heat one end, and make sure the other is at least below 79.
Get rid of the fogger. Too much constant dampness can cause the symptom you are describing. 3 week old veileds in a tank that size tend to do best with a hand misting of the enclosure a couple times a day and possibly a drip cup, depending on size of the babies at this point (without a heat light and at those temps, and because it sounds from your description like they are still mainly eating fruit flies, I suspect yours are probably still pretty small, and the misting 2x or maybe eve 3x per day would be fine). If they haven't grown much since hatching, you may want to mist enough that water drops form on the glass, branches, and leaves, but not puddle at the bottom, and then let the enclosure dry completely, and then mist again a short time after it completely dries. I do that for the first couple of weeks normally. Constant dampness causes problems. Once you have babies with eye problems like that, you may need to make sure you hit the babies slightly just a little (like a pump or two from a hand-held mister) with the mist to get them started drinking and to get their eyes open. Once eyes are open, offer food a short time later- make sure it is well gutloaded and dusted with supplement.
Find out for certain what brand flourescent you are using and report back. Improper full spectrum lighting can cause the symptom you are describing.
I have no experience with the t-rex powder, but again, lack of adequate supplementation can cause the symptom you are describing. Maybe someone here knows about that supplement. But lack of proper nutrition or poor or inadequate supplementation can definitely cause the symptom you are having...
Basically, get some good info and then check each point with your setup to make sure you are following each thing exactly. Light, temperature, how water is provided, supplementation, gutloading, all of these are very important and you can't fudge them or you will end up with more problems (google is your friend, try to get a care sheet for babies from a breeder somewhere that gives brand names for supplements and lights and go point by point through the sheet and make adjustments to what you are doing so you are doing what the breeder is doing as exactly as possible).
You should also spread them out some by this age- splitting them into 3 enclosures about the size of the 10g would be better by this age. Stress from siblings that are outgrowing them or that are more territorial can cause the symptom you are describing.
The symptom may be caused by different problems. The only way to troubleshoot is to go step by step and check everything you are doing and make adjustments.
