First time growing lettuce under lights. Using LED's with a few different color arrangements in different areas (Cool white, Warm white and Red/Blue) as a test. Everything started off great, and I got a complete first harvest- Spinach, Arugula, Butterhead, red, mustard, Romaine. I have been picking the big outer leaves and letting the small leaves fill back in with each harvest- not cutting the entire plant.

But, strange things are happening! The Arugula and Mustard are forming these very thick, leathery leaves. Arugula have gone to dark green, Mustard look right but are very thick. I chopped back the Arugula and am now getting fresh green leaves in the center but fear they will go dark and thick too.

The Romaine, Red and Butterhead are all still doing great, I have harvest each 3 times and they grow back well each time.

The spinach went pretty dormant. The leaves all started yellowing and growth is crawling now. One good harvest, nothing more for a long time. Nice fresh green leaves in the center forming but don't seem to grow much.

I am growing all of these in 4" pots, watered from the bottom in soilless mix from Johnny's. I have applied fish/seaweed fertilizer twice now- every couple weeks. They are all about 6 weeks old now.

Appreciate any thoughts you may have of what is going wrong. Theories I am working on now are:

I let them get too dry between waterings, slowed growth. Now watering more frequently- every other day.

Pots are too small. When I transplanted my tomatoes and peppers from the 4" to 6" they started thriving again- maybe same root bound problem? I don't really have enough room for 6" pots for everything. Hydroponics in my future but not ready to go there yet.

Thanks!