Leaves still not improving... HELP!

Ok I thought I had a mag def but things seems to be getting worse on most of my older growth. I added some epsom salt to my reservior 3 days ago and thought things were getting better.

Temp - 65F
PPM - 650 (Fox farm hydro nutes)
PH - 5.8

Once they are damaged from a deficiency like that do the leaves continue to get worse?





What does it look like to you guys?

The thing that has me scared is some of my newer growth has some small yellowish/brown spots appearing as well.

Thanks!

anyone think it's still from a Mg def? Should I try a bit more epsom? I added 1.5 tblspns to my 12 gal res so it was about 1/4 per gal