Not a lot of information, but it seems some nutrient block. Did you check your Ph? Last run I experienced Ph issues, with consequent nutrient block, which look like in your pictures.
With wrong Ph the plant is not able to get nutrients, and try to absorb them from the reserves in the leaves, which turn yellow, brown and then die.
If you didn't I suggest to buy a Ph pen and make sure to fit the range (I go usually around 6-6.3, which is also good for Calcium)