I too experienced drooping im the past and tried everything to fix.
One thing that no one else really picked up on was the 24 hour light cycle i was using, the light intensity, and the size of the plants.
If you look at your DLI (Daily Light Integral) versus the health and size of the plants, you might find it's just too much for them?
Basically i was hammering them with too much light and not giving any time to rest. Once i reduced the light and switched to 18/6, they perked up on lights on and started to droop before lights off (ready for sleep, i guess).
Even with a 65w hlg light i was hitting a DLI of 38, which was too high for my small vegging auto. Once reduced to around 28 it looked happy.
I have some links for lumens to ppfd and then ppfd to dli conversions, you just use your phone with a lumens app and then do the conversions to get a ballpark DLI.