I have couple of plants in "soil" and both plants have this issue. What do you think is causing this?

I am using RO water, cal mag and all the botanicare mixes. I am following amounts on label to mix in so just a little strange on what is up with these spots on leaves. Plants are 5 weeks into flowering.
scottcc5s Reviewed by scottcc5s on . 1st ebb/flow grow OK guys the day has finally come and I hooked everything up and jumping into the deep end of the hydro pool so to speak. I appreciate info from those that have help to this point. Not sure how it will work out but here goes. Specs of my grow: 1) 12 plants in my ebb / flow setup. 8 Super Lemon Haze and 4 OG Kush. All FEM plants 2) 600 watt (400 watt and two 90 watt LED's for later) 3) Grow tent 6x6x6 4) RO water and trying to keep it in the 5.6 to 5.9 PH range. PPM right now at 630 5) Rating: 5