yep those are new roots he needs more soilIn the last picture, are those roots?
I think you would really need to fill us in on what your planting medium is, if you are using fertz, what lighting you are using (as in lumens and Kelvin) and what ever else you can about your grow, before a good educated guess can be made. Some of the symptoms can be guessed at that are present in the picture but there are multiple problems that can show the same symptoms as well.
no dirt is too acidic ... as soon as you change the dirt spay then with epsom salt.. they will turn green and look much better
Dont get all fancy. They are good except for what Judy said. Give them a shot of Epsom Salt. I usually do a 1/20 mix, sometimes a 1/10 mix. Foliar feeding is the quickest way for them to get their nutrients.