Discoloration on leaves. Need help diagnosing the issue

My girls are about 6 weeks old there all female gg from seeds. They have had no issues until now just starting on the smallest one. There’s a slight discoloration on the new growth of a top, turninng yellow. I think it’s a nutrient deficiency because I haven’t been able to feed them the last few weeks. It’s been raining and the pots haven’t dried out and I want to prevent over watering them. I also noticed the other two plants tops look more yellow then usual. Can someone please help me figure out what there deficient of or other problems they might have.

Starving
Even overwatering with nutrients is better than starving the ladies

Hmm not sure. Except for those leaves plant otherwise looks okay... I'd probably just keep doing same unless it's spreading, not sure...

Iron