First off, welcome
Check pH, what are you fertilizing with, how often, how often do you water?
The leaf tips look burned
Take a close-up of the leaves
I agree with herr_gruen that you need to monitor your pH. If your pH is good then what and how much are you feeding it? What medium are you using and what are your environmental factors, like temp and the rh. Once these questions are answered we can give you much better advice. Until then all we can do is give educated guesses.
Thank you for the quick reply and the information. I will first take care of the pH. Kind regards.
Thank you for the quick reply and the information. I will take care of it immediately, and yes, the light needs to be higher. Kind regards.
I didn’t mean the lamp, but a possible nutrient burn. If the lamp is too close, the leaf fingers fold upwards, and there are white spots on the serrations of the leaves. I couldn’t see any of that. Take a close-up of 2-3 of the damaged leaves; based on the damage pattern, one could also determine the cause, as each cause has different effects
It has a clear nitrogen deficiency because they are yellow, likely due to a bad pH, but beware
I would also have to lean that way. You will not correct to leave that are already yellow but keep an eye on your new growth when changes are made
Also, visibly on your photo, the humidity in your box seems too dry; it should be around 45 to 60%.
Hello fellow growers 
,
Since everyone is already giving their two cents… 
Also a warm welcome @Kiffer62 from me.
Well, I also see a nutrient deficiency… Something bad (too dark light)… Maybe the pH value is shot…
But
I’d say he’s already smoked it, considering the date of the original post in September 
… I guess I have a bit too much 
It was only shown to me as “New Topic”… I must have overlooked the timecode. 
Well, I just hope he/she/it could still save something.