Your spots are cause by a calcium/magnesium deficiency.
Add enough to the RO water to bring it to 250ppm. then mix your nutes , let it sit for a while, then test/adjust the PH.

Don't sweat the Chlorine, or the Chloramine.
It's actually good for the rez.
Kills slime molds and fungus without even annoying the girls.

The old damage is permanent but the new growth should be OK.

2 cents, please.

Aloha
Weezard