I have the same issue, was thinking that once the foliage shades the soil it will be better .. and the lights are higher? The dark soil really retains the heat from the lights. I am using the same bulb/fan setup ...

I'm really new to this; but I've run into the same issue with just a T-5 - 4 bulb, 4 ft fixture. I have a fan running, and cracked open some ventilation on the humidity dome. But that just dries it out even more. I've just had to be diligent with the water.

50/50 verm/peat moss mix

Why are you using that for growing on? It is just a germination mix at best.

I assume these are off the heat mats and the domes have been removed?

Dave

Any potting mix will dry out quickly when under warm lamps and in a constant breeze. Never let it dry out completely. A home made mix doesn't have a wetting agent in it so it will be more difficult to get it wet again once it dries out completely. Bottom water and give it time to absorb. Adding a water retention product would help.