Need some advice - probably over fertilized

Hi everybody, I'm a first time grower and I believe I probably over fertilized my plant, I'm growing on hydroponics (ebb & flow) and using a 4 inch rockwool. After I saw the burned spots, I already flood my table with my plant with just plain water, however, the spots continue to appear, fortunately I don't see burned spot on the new leaves, however I'm not sure if will continue like that.

So, I would like to know what should I do, should I continue just using plain water? For how long? Another question is, since I'm growing on a 4 inch rockwool, how many times per day I should flood my table?

Thanks

don't think that is nute burn, that usually starts at the tips, are you using distilled water?

Those spots are a calcium and magnesium deficiency. Either do to lack of the nutrients in the system or pH is off and is locking out those nutrients .

Plain water with hydro will kill them, slowly but surely. My tap water is 7.0, which is neutral, but deadly to a hydro plant. With Rockwool especially, you HAVE to maintain 5.7- 5.8. No higher or your nute uptake will be affected greatly. Also you MUST de- chlorinate your water for healthy biological to be created in your root systems.
Normal nutes or lower won't hurt. DO NOT FORGET CAL MAG, and really watch your PH. Good luck.

I was using tap water, and I adjust the PH to 5.5 to 6. The reason that I thought it was over fed it was because those spot started to appear when I use the same water that I use to feed my pepper plants. However, I've just check the PH and it was a little bit high - 6,5 and the PPM it was 660, which I believe it's not too high.

Thanks guys

what is the ppm out of the faucet ,just asking and wondering how much PH down you are applying to get it to 5.5 ,it definitely looks like it needs epsom salt or cal mag which ever way you want to go ,also check your ec .