Ph problem?

yes, it looks like ph issues, how high was your run off? ph 7 is not good for the plants, usually it should be between 6-6.7 (for me it works best around 6.3-6.5). Try to flush it with water in this ph range. and dont forget: the damage on the plants won't go away, you see that the flush works when theres no more new damage on the leaves, plants dont "repair" the already damaged leaves. happy growing <3