I know there might be millions things causing thes...

hi there Haftanara, i can confirm that it's surely not N toxicity which you can from dark green leaves and glossy shine. It's not calcium problems which are more "spotty" and it's not magnesium which is more uniform around the edges of the leaves. It's could be PH fluctuations , certainly it looks exactly like it, but what i do think it is, is root problems that look like pH fluctuations because we're also seeing that leaf cupping and leaf curling ... and, you know... brown roots ! so what you can do is get something like some hydroguard, up the enzymes a lot maybe up to 2 , 2.5... or what i think will help the most is a technique called root pruning. Root pruning is when you cut all the unhealthy roots off, carefully. This technique is very effective at stimulating growth, so you'll actually see faster and more vigorous growth ! what you do is simply cut off any brown dark brown roots, until there are none left or until a maximum of less than 20% of the total root mass... then wait and see how great it helps ! you can repeat this once a week once every 10 days, up to you and up to the plant, but you wont be stunting it's growth, on the contrary, the plant will thank you for it ! does this make sense ? hope this helps ! 🚀