Under watering or over watering

I would guess it could be heat stress also...

I agree with Organoman, 24/0 is to much. key takeaway. Overwatered = Limp leaves + Stiff Stems Underwatered = Extra Limp Leaves + Limp Stems Good Luck!

looks dry. watering is simple. fully saturate, a little runoff with soil won't waste too many amendments to ensure that it is. Wait for top 1" to dry and repeat. With a smaller pot, maybe top 1/2" then re-irrigate. Rinse and repeat. If you get any droop doing this, use more perlite (or similar) next time. If your soil has a good air/water mixture, it is impossible to overwater in any common sense circimstance, if adhereing to the SOP above. if you want to irrigate/fertigate more often in flower, you can trigger your 'next' irrigation a bit sooner, but you have to make sure some minimum "dryback" occurs in the substrate. So, if the plants can't drink it fast enough, that makes more frequent fertigation more difficult to do. if giving 24/0, as organoman pointed out, that can definteyl cause droopiness too, if giving too much DLI. Read the wiki on daily light integral. Get the gist of it. You don't need to memorize the math or anythibng... rate of photons x hours = energy given. If you give the same amount of energy over 18 or 20 etc, it will have similar results in growth. Giving more than it can process per day will only hurt the plant. With ambient co2, 35-40 DLI is a ballpark max you can give. Reference your lights and you can guesstimate the amount of DLI you are providing for various hours of operation... observe plant and adjust as necessary (e.g. internode length is a good guide for light intensity) Also, if they are incredibly droopy for long periods of time at end of day, that's another sign of giving too much. Plants droop during the day, so if you see 1.5 horus of constant droop leading to lights out, good sign you are giving a bit too much. too much light doesn't always show a symptome right away.. it can often takes weeks of giving slightly too much before you see something like stunting or burned pistils. keep notes, because you may need to reference as much as 30 days prior to fully understand what has happened.

Yes, looking thirsty. Also looking exhausted from growing at 24/0. NEVER grow at 24/0..........18/6 is optimal. ALL cannabis plants NEED "sleep" for a correctly functioning metabolism. There are certain metabolic processes which occur during the dark period that can not happen during the lights on time. Without a light/dark schedule the plants can not do these processes, leading to incomplete photosynthesis and plants that are not growing at their fulll potential. 24/0 is the biggest "lie" when it comes to cannabis and can only be recommened by people who do not understand photosynthesis and/or how plants function correctly.

The stems on the fan leaves look like they are ready for water. That's what I look for to know when they are thirsty. The way they droop and get that curve in them.