Plants get droopy half way through the day

Maybe they really had enough light. I always observe this at the end of the day, about 1-2 hours before the lights go out, that they want to have some peace. The next morning, they're back to being fit. But I only have 150w, not 600w. Maybe it helps to lower the intensity of the light since they're in Veg anyway and don't need the full 600w.

In my belief plants wake n sleep as humans do.when they droop I believe there due for a sleep cycle and are clearly indicating they have finished there days cycle and ready for rest.

Some believe cannabis plants have circadian rhythms. Does it happen precisely on 12/12 schedule? Cuz this happened with my first grow. I knew to take pictures at 11am because that's when the leaves looked most "awake". She was an otherwise mostly healthy mini-monster of a grow, so I chalked it up to circadian rhythm. Guess I'll never truly know. This did not happen with my second grow, however. She looks great, btw, Good luck!

The drooping could be caused by plants losing moisture through their leaves. This is a natural process called transpiration. Plants that have adequate moisture may droop in the daytime and revive without assistance as the temperatures drop in the evening and the plant's system balances out.