Leaves shrivelling/ curling up

Überwässerung kann gut sein. Aber ich tippe eher auf völlig falschen Lichtabstand und Lichtstärke.

They look heavy to me, and puckered. I'd say overwatering

salt toxicity... reduce fertilizer concentration significantly. In this case you may want to flush with a bunch of runoff and then wait and see before acting further. it's tought to know if you should do that immediately or if you should wait for it to dry a bit first... the problem with the latter is that it continues to uptake high concentration of dissolved nutrients. The problem with immediately doin it is it looks like you have watered too frequently already. in this case i'd err on the side of reducing nutes... let it dry until top 1" is dry... feel weight, wataer at that weight from now on - whether fertilized or not. for the intial irrigations after any flush, i'd make sure to get 10% runoff... this will ensure you aren't raising EC/nute concentration of medium. after that, if soil, just enouogh runoff to ensure it is fully saturated -- recurring dry pockets are bad news.

At this age I doubt it's a deficiency. Looks like to much water or to much nuits. Cut back on both. Only water when the pot feels light and give less nuits.