my lower leaves are turning yellow

[indy]

I started my 11 plant garden last week....my ppm is 420....my lower leaves are turning yellow...I assume it is low in magnesium and my ppm should be higher (is it?). I am growing tomatoes (sorry). My ph went from 6.1 friday to 7.2 today also. I plan to add some epsom salt in the morning and increase my ppm. I love this site and thanks for sharing your knowledge with us..........indy

[Ron]

Yes your ppm should be twice that and lower the pH every day (if you have to) to keep it in the correct range.