It's normal for the plants to be drooping a bit, before the lights go off.
That shows that it's their time to rest.
I used to keep the plants on for 24hrs and I've noticed that most of them get "tired" right before the 18th hour of daylight.
So that's why I decided to switch to 18/6.
I have controllers on my lamps so I keep the first 4 hours at 25% then I move to 50% and 4hrs before I turn them off I go back to 25%.
That's what I do in early veg and moms, late veg the 50% is longer.
Even outside the sunlight isn't always at 100%.
This method has been working very good for me over the years.
When you reduce the amount of light cannabis plants receive, you reduce growth. Similarly, when you increase the amount of light plants receive, you increase plant yield, plant quality, crop yield, and crop quality. This assumes, of course, that light is the limiting factor.
Per Bugbee, there is no research that indicates value in gradually increasing or decreasing light levels. Some light manufacturers are introducing that feature in their systems and I see that as a means of differentiating their product from others and, in the highly competitive marketplace of grow lighting. That's needed because grow lights are now a commodity product. There is no evidence-based reason to increase or reduce the amount of light, as if to mimic sunrise or sunset. As Bugbee says, plants "are ready to get to work" as soon as the lights go on.
Re. photoperiod - Growers refer to lights out as "the dark period" but, in plant biology, "the dark period" has nothing to do with the time when the lights are off. The "dark period" in plant biology refers to processes in the plant that are not light
dependent and those processes run whether lights are on or off.
Cannabis does not need a "lights out" period to grow. You can grow cannabis for as long as you like using 24/0, or any combination of on/off, and the plant will remain in the vegetative state as long as the amount of light it receives is > 12±hours. Again Bugbee ("what with this Bugbee shit!?"), when asked about the 24/0 photoperiod, replied that a 20/4 schedule would give plants a "rest". Rather than use my interpretation, I'd urge you to watch the video, another segment which I discuss next.
IIRC, Bugbee addresses the idea of a "tired" plant in a video interview that he did with Dr. Growit on YouTube. It's one of the questions asked at the end of the video, when Growit is reading questions that viewers have asked in the comment section. Per Bugbee, there is no evidence-based reason why plant behave in that way but the operative theory is that plants are reacting to sunset and they are lowering their leaves, perhaps, in an effort to trap air so as to keep the ambient (warm) air. That is based, perhaps, on the fact that photosynthesis rates tend to increase as temperature increases.
Conversely, there is no research that indicates that leaves drooping is a reaction to excessive light. The symptoms for excess light levels are well documented, the most common one being light avoidance, which typically is done by rotating the leaf around the axis of the petiole, by the petiole elevating to a high angle, or by curling the edges of the leaf ("canoeing" or "tacoing"). In one of my grows, one cola was getting too much light (950µmols±) and it bent at a slight angle couple of inches down the cola.
Light avoidance behaviors are exhibited by the inflorescence closest to the light source. Light levels drop off very quickly so light avoidance is, generally, at the top of the plant and is tends to be very localized.
If the OP want to resolve the malnutrition issue, he should be getting the plant to the light saturation point as quickly as possible.
