Curling and cupping of leaves! ADIVCE NEEDED!

i Have 5 plants growing under a 400wHPS light which is now on the 7th day. The temperature reads 20-25C with a humidity of 40-50% with the lights on, when the lights are off the temperature is at 15-20C and humidity jumps to 80-90%. Two plants have some serious curling of tips of many leaves all over the plant along with some cupping of the whole leaf of the bigger leaves. here are some pictures, this has been going on for the past 9 days maybe and is slowly getting worse. Any advice, tips, something to check for on the plants, would be greatly appreciated!

too much N

Stop feeding them nitrogen if you're still suplimenting, check that you are not over watering. I would get some fungarid and dose them with that in case you have something going on with the root zone.

I'm thinking too wet.

I have found in pure coco that my plants drink less for the first week or so after switching to 12/12 but that could just be me.

how do i take out Nitrogen then, I'm not adding any nutrients to them yet?

my advice is let them dry out real good, stop everything, they will perk right up.

I'm seeing very similar symptoms on the plants we put into flowering. I had seen another thread where someone posted pictures and the replies all generally said magnesium deficiency. I started foliar feeding the plants with and Epsom salt/distilled water mix. One plant completely recovered. One showed improvement but hasn't fully recovered and one had no change. However after reading this it makes me wonder if I have nitrogen toxicity. Very interested in seeing what is causing your symptoms and what fixes it. If it is a nitrogen abundance, if I'm not mistaken, I believe a good flush and then adjusting its feed would resolve it.

older Leaf tips curling down. Leaf margins curling under. older leafs turning yellow.
(Use your flash next time when your lights are on. You'll get true color of the plant)

Phosphorus deficiency will make your leaf tips curl under.
Nitrogen toxicity will also make your leaf tips curl under.
IMO- your leaves are not lush green, I don't see signs of (N) toxicity leaf burn.
You have a Phosphorus deficiency.

Phosphorus deficiency will make your leaf margins curl under.
Potassium deficiency will also make your leaf margins curl under.

IMO- check your soils pH, check your feeding schedule.

Good Luck on Your Grow.

I agree with Topfuel, check your ph.
On a side note, the high humidity situation needs resolved as well.
Happy gardening.

I would advise flushing your plants to stop them from dying out unless you want to have some shitty buds