i know everyone answered this but your plant needs nutrients. A lot of times soil comes with nutrients and you dont have to use othr nutes until 4 weeks in. It looks like you need to give your plants proper nutes. Flora Micro,Grow,Bloom&CalMG is all you need. Make sure the PH is always always always between 6&7, I do 6.5. Your plants will respond once you give nutrients. When you see the leaves losing the dark green color that means your plant is starving&using the nutrients in the leaves to survive.IT does not look like that bad of a problem,you can get it under control if you do that-Also make sure your plants r the correct length from the light,