Nutrient deficiency?

I think what you are seeing here is just a fresh new leaf. They will always come out slightly down colored then green up over time. Dr. Bruce Bugbee went over this in one of his videos and the the reason behind this is simply because they have not been able to produce enough chlorophyll yet to turn green. This is especially true if your go into your grow room right as lights come on and all the new growth is yellow because they have had no sunlight yet. I would keep doing what you are doing because the plant looks healthy. The level of light you are giving it now is perfect till you are ready to send it into flower. I hope this helps.

A little over fed, not under fed if anything. Try adding some cal/mag to your line up, it does look a bit like a developing magnesium deficiency. Next time, consider growing less plants and using bigger pots in youur small space, LST can control the plants and the bigger pots will help prevent any issues with nutrient salt build up in the substrate. Small pots can become toxic quite easily, especially if the plants are not watered to run off adequately each time they are watered/fertilized.

A little over fed, not under fed if anything. Try adding some cal/mag to your line up, it does look a bit like a developing magnesium deficiency. Next time, consider growing less plants and using bigger pots in youur small space, LST can control the plants and the bigger pots will help prevent any issues with nutrient salt build up in the substrate. Small pots can become toxic quite easily, especially if the plants are not watered to run off adequately each time they are watered/fertilized.

I think you backing off the light was a good call, the growth looks quite tight. I also agree that new growth can be a bit yellow.green and if its greening up later its nothing to worry about. I don't see anything that's crazy for deficiencies, keep up the regular feeding and adjust if its showing any other signs of to much or not enough. Yellow from the new growth from the inside can be a sign of S or Fe not being absorbed right but I don't think this is that. https://420life.com/wp-content/uploads/2021/10/Marijuana-Leaf-Deficiency-Chart-scaled.jpg This chat is nice for looking up leaf symptoms but diagnosing is another trick. if it caused by lack of something or is it locked out from to much of something else or wrong PH. Good Luck!

Sometimes new growth can start a little pale, especially when it's growing fast. Does the new growth darken up as it gets bigger? Think you're fine. Plant looks good.