PH is probably off causing lock-out of MG/CA (or whatever) or toxicity of N (or whatever), as they say if you have any problems in soil/hydro fix your PH FIRST. Run PHed water through there on this next flush, check the runoff (so if you run 6.5 through and get 7.5, that is bad, if you get 5.5 that is bad) - there are directions around and you can be the judge on what your soil Ph should be looks like around 6.5 anything below that you lock out P,CA,MG in soil - seems the problem to me.
https://www.rollitup.org/marijuana-plant-problems/133385-ph-lockout-guide.html
GL,
z
Both of these leaves in figure 3 and figure 4 are from the same plant. It could be over fertilization, but more likely it is due to the pH being off. Too high or too low a pH can lock up nutrients in the form of undisolvable salts and compounds, some of which are actually toxic to the plants. What then happens is the grower then tries to supplement the plants diet by adding more fertilizers, throwing off the pH even more and locking up even more nutrients. This type of problem is seen more often in soil mixes, where inconsistent mixing of the medium's components leads to "hot" spots."
