1 thing i should mention, watch the damage on the leaves to see if it progresses but old damage doesnt heal. Its not uncommon for old damage to look worse once youre fixing the problem. Iif the damage was bad enough those parts of the leaves are dead and youre seeing that, be careful you dont confuse that with still having a problem. If the damage isnt spreading, then youve got it fixed. I have a strong feeling that its a mix of magnesium deficiency and poor watering practices. Get those 2 sorted out and they should recover just fine. As a suggestion, even if you arent seeing problems with the other plants yet, you should check them too. Magnesium deficiencies take time to show and its possible they just arent showing yet. Im only thinking about the other plants too because your runoff was a higher ppm than your input and im going to guess you were feeding the other plants the same way. So if you havent yet, you might want to check the others too.