I've been raising tomato plants from seed for a decade, but this year I invested in some LED grow lights because I was out of room under my florescents where I started the seeds when the time came to pot them up. The LEDs are Mars Hydro lights, one is about 140W "true power", the other is 205W, including some UV. I've notice some of the tomato plants have leaves that are curling and turning yellow. I have not been feeding them because I just potted them up using an organic Pro-Mix and I think that has enough nutrients for a while. I've notice the yellowing and curling are worse for the tomato plants that are more directly under the larger light. So, I turned down the light (turned off the blooming switch) and raised it a bit and rotated the plants around. I also reduced the numbers of hours per day they are getting light from 16 to 13. Looking at the picture below, which was taken April 18, the plants are much bigger 9 days later, so in general they are doing ok. But, what to do about the yellowing and curling? Maybe also water less? Incidentally, my broccoli and cauliflower (which need to be planted outside) and the peppers are doing really, really well.