I dont think they read the whole post, I was confused too when u say they drop at night, but u mean your night, as the plants dont have a night at your house right now.
I keep my lights on 24 hrs also and they are perked up all the time. Do u water right before they do it? Do the temps change? If u keep lights on there is no night for plants, they have no idea what time it is. They are steadily transpiring and producing sugars at lights on. Something has to be changing in the environment for them to do this, most likely u are overwatering them and by the am the excess water has transpired and they are happy again.