Having grown under 4' shop lights for decades, your plants need to be closer to the tubes, for one thing . . . I recommend moving the plants up to the light rather than moving the light down to the growth. Allows for different size plants getting equal light, under fluros.
The ends of the tubes get hot, so place vegetation accordingly.
The yellowing is lack of enough N, IMO.
I've taken to always doing a nitrogen boost feed just as I go to 12/12.
Below's a 3 week old plant grown under fluros close enough for decent growth. This is 6-7" tall.
