From what I see of the roots, that is discoloration caused by the calmag+. The roots themselves look healthy above and below the parts that are tinted brown, however, keep an eye on them, you've got all the right conditions for root rot so you should avoid that at all costs.

Additionally, Zandor is probably the best qualified to give advice. I would recommend you listen to him more than the rest of us

GM
GluteusMaximus Reviewed by GluteusMaximus on . Identifiy the problem ~800 PPM CalMag + FloraNova Grow PH @ 5.6-5.8 at all times -- Skunk #1 -- These are clones under @ a little over two weeks of vegging - I did find algae in the res, so I changed nute solutions last night -- They are under 18/6 cycle -- Plants are getting progressively worse as time goes by. This seems to mainly effect the fan leaves... Rating: 5