Hey Timon,
It looks like your plant might be dealing with some pesky little critters, probably something like thrips or spider mites. They love to snack on the leaves, and that can cause the kind of damage you're seeing. If you haven't accidentally damaged the leaves yourself, it's most likely these pests causing the issue.
I'd suggest checking the underside of the leaves to see if you can spot any tiny insects or eggs. Neem oil is a solid option for dealing with this kind of thing, or you could go with an insecticidal soap if that's more your style. Just make sure to get good coverage when you spray.
Also, improving air circulation around your plants can help keep these pests at bay. If you can, try to increase the humidity a bit too—spider mites, in particular, don't like it too humid.
Keep an eye on it and hit me up if things don't improve. Much love from Germany, bro! 👊
Cheers!