hello,
I think it could be a little bit Nitrogen but also some other problems as well. I think I'm seeing, magnesium at the bottom, potassium and phosphorus maybe. Are you giving any nutrients? If not id say you might want to bring in some sort of bloom/micro/calmag, but id also double check the accuracy of the ph, your light distance(maybe its giving out some stress too) and also your watering practices(any muddy soilhappening? ). Examine a few possibilities and see what might apply to your environment.
I know that is a lot of possibilities but sometimes it's hard to pin down without so many specifics.
Happy growing. ✌️