What's the problem with this plant?

first couple set, even first 3 sets of leaves can look fugly and then be pretty after that. could be something out of balance or too strong for a young plant. would need more info for that and encyclopedic knowledge about the products you use to have any confidence. If you continue to see this sort of thing, then i'd look to the pre-charge of the substrate or fertilization choices you made. A lot of esoteric fertilizer formulas out there "can" work but won't work for all plants, then people blame the plants instead of the formula / ratio that pre-existed in the substrate. As long as new growth is better, i wouldn't worry too much about this 1 plant.

Hi :) sometimes genetics have some issues. Often in the following nodes the leaf appearance is getting normal and it’s just the first 1-2 pairs of leaves. I‘ll just wait for the next ones to see if they look alright… :) good luck with your grow!