Yup you can supplement with epsom, I do. I foiler feed and add it to res when in flower.As i believe it, the big worry is if your water has too much calcium in it, those ions will lockout whatever magnesium is available.
I'm not sure if supplementing magnesium (epsom salts) to bring it back to an appropriate ratio will rectify the problem... Have you googled this? I remember there being a ton of info out there, just can't recall the specifics.
Lol. Mineral water, with mostly mineral. How long was the RO membrane last ing?77 gpg is roughly 1316 ppm...........
Are you sure that’s correct? Whats your health department think about that?
- Jiji