What happening with my leaves

Hi please can someone help me with the issues I am having with my leaves this is happening all over the plant but mainly the older leaves at the bottom but there are some closer to tge top I had a issue with low humidity but I have now resolved the humidity problem but the leaves keep turning like the picture any advice will be much appreciated thanks all

That is some leaf necrosis .... We would need more info of the grow you are doing ....

Nutes
Medium
Ph
Water
What you feed ( amount )
Etc.

that looks like a bad P deficiency to me.
it would help a lot to know what kind of medium you're using, what the temps and ph in your grow room are, what you're feeding them, what the ph of your feed is.....

Thanks for the replies guys I will tell u as much as I can if i leave something out just ask and I'll do my best to answer it

• Plagron Terra nutes (power roots ,pure zym ,sugar royal and had a couple of feeds of the grow as they did not call for the Terra grow for around 3 weeks)
• Medium is plagron lightmix
• Ph is always 6.0 to 6.5
• Just tap water no RO
• They are now on full strength power roots and pure zym and the last two feeds have been the recommended dosage of the Terra grow
• Plain water for first 3 weeks ( lightmix soil has feed in already)
• Sealed room
• Mini split AC
• Humidifier
• Dehumidifier
• 800ppm co2
• 25 litre pots
• Temps 28 day. 23 night
• Humiditity was 27% day 75% night but now have humidifier and it now sits at 50% to 68%

Thanks guys look forward to your replies

lightmix is peat, which is very acid.
i'd bet your root zone ph is low. gather some of the run off water the next time you water and check its ph. if its very low, raise the ph of your feed water to counteract it. you might consider adding a little lime to your mix the next time you start a plant.

i'm not familiar with those nutes, but if they're like almost every other manufacturer on the planet, you can probably cut their recommended levels by about half, and still be overfeeding a little

also, on the plagron lightmix webpage, they recommend not starting seeds in it, and not putting seedlings in it till they're two weeks old. they say the fibers in the mix can get in the way of the roots growing