Deficiency

I see at least 2 issues one with the light and the other with nutes, maybe calcium... Double check your env and your soil...

Your diary says both outside and 5cm light distance yet photos in a tent. On that I would say you mustn't have the correct details on your diary as you have plenty finished grows to show you can grow But The seedling that's top heavy and the bushy minimal internode distance makes me think the light is very close

I'm pretty sure it's mainly a magnesium deficiency, with a slight deficiency of calcium and iron, too. To treat this use CalMag and a foliar fertilizer (like Plagron Vita Race), because those work the fastest, since they don't have to be transported all the ways from the roots to the leafs. Hope this helps 👍 Cheers💪

pH could be reason for the discoloration and combined with a light thats too close some leaves are burned i guess. 5cm is waaaaay to close especially for youngs plants. go for 50cm