Can someone explain to me why my plants are always tired in the evening, about 4-5 hours before the lights go out?

We got it solved over on my discord.

They droop at night because there is a lack of light, so they don't react with increased turgor pressure, which increases surface area, but that costs the plant energy to do so, therefore no reason to do it in darkness. The plant has no central nervous system. It simply reacts in a compartmentalized way to the environment. You can turn the lights off at any point and see this in action.. then, turn them back on and it should spruce up. Plants can oscillate a bit during light hours, too. So, any short-term droop is less likely a problem. If your app is accurate, 29 DLI is far too low to cause such a thing. The +/- error percent of that app should not be large enough relative to "29," but I can't say for certain. If up near 38-40 DLI and higher, light issues are possible with ambient CO2 conditions. Any DLI measurement from a phone is suspect, because it is just a poorly converted klux measurement. might as well use the more accurate lux readings as proporitonal intensity for leveling out spread of light because there is no conversion error being interjected, needlessly. if severe droop is every single day for multiple hours specifically at end of day -- probably too much light. Should see other signs over time, too. Nodes will be too tightly packed, more dramatic leaf wilting, interveinal damage at top... So, as long as growth is normal, don't worry too much about it... if it's for ~2 hours every day at end of day, raise lights an inch or two or reduce power 5-10% and see what happens. It may take a few days to snap out of the behaviour, so if you do "something" give it time to react to it.

gottagrowsometime@ Can you provide a reference or a link to a video or paper that explains the correlation between DLI and plant droop? I've never heard of that correlation before.

Its all about DLI. A pheno can only take a certain DLI level. I've 1 auto that can only take 14hrs of light and she starts dropping. Yet, I've so many plants. I can't stop my 17hr, so after 14hrs I put her into a dark room. Point been. Some plants especially at different stages. Like pre flower, you gotta be careful not to push the stress level too much, but in fatthing they'll always want that extra DLI (PPFD) So find you balance and be one with the force.

They sleep, aka rest. If you had night vision cameras in your grow you'll think holy fuck drought! But about 3 hours before lights go on, take a look, they are awake and perky and just waiting for that light energy!

This has happened to me a couple times. My plants were super healthy, but they dropped entirely way too early. Around the same 4 to 5 hours you're getting. For me it was the light intensity. Too bright and it was causing a bit of an overload. Try dropping your light intensity or raise the light up. You should see a difference overnight if that's the case. Hope this helps.

Slight droop is totally normal during parts of the transpiration and respiration cycles. Totally different than environmental caused droop like overwatering.

They are most likley getting ready to sleep if you have the same routine plants are very photo sensitive. no they arnt camera shy lol they just like good light routines. they look completely fine to me very healthy i think you should just carry on doing what your doing buddy. leaves will often droop when the lights are off if you look at time lapse videos you can see this in action :) its completely normal :) best of luck and keep up the great work :)