I bought some Cal-Mag+ and added 2.5ml/gal to my water yesterday. I was unsure of concentration, so I started small. The back of the jug gives a desired range of nutrients for a hydro system and then says what 10 ml/gal of cal-mag plus would add. From back of Cal-Mag+ jug:

Desired:
N: 160-250 ppm
Ca: 160-280 ppm
Mg: 45-75 ppm
Fe: 2-7 ppm

10 ml/gal of Cal-Mag:
N: 53 ppm
Ca: 84 ppm
Mg: 31 ppm
Fe: 2.6 ppm

I don't have a EC meter, so I can't check my resevoir ppm levels, but wouldn't that just give me total ppm and not individal element concentrations?

I'd like to calculate what the elemental concentrations from my GH nutes would be, but they are listed as a %, not a mass or concentration. Is 1.5% the same as 15,000 ppm? So, if I add 15 ml of florabloom, and it has 1.5% Mg, to a 3 gal resevoir do i get 19.8 ppm Mg?

(15,000 ppm)(15 ml) = (x ppm)(11,356 ml) [11,356 ml = 3 gal]
x = 19.8 ppm

Is this the correct way to calculate this? Also, if I got an EC meter is there a way to measure individual ion concentrations or is it just total disolved solids? And what good does knowing TDS do if you don't know individual ion concentrations?

Lastly, I'd like to use the Cal-Mag+ to foiliar feed the one plant that is sick. What kind of concentration should I use for that?