Hard to tell without pix, but I would guess overnute, ph, or roots not being allowed to dry between waterings. (ferts + MG Moisture Control = possible overnute) But shitloads of potash in the nutes could be bringing the ph too high. Might be overwatering. (they call it moisture control for a reason, lol. It retains moisture)
Filling-out the troubleshooting form would help narrow the possibilities.
Rusty Trichome Reviewed by Rusty Trichome on . 2nd Grow: help leaves changing colour Plants are 3 weeks old. The soil is miracle grow moisture control. Watering every two days. Light 200W veg envirolite. Only started using nutes, Plagron Alga grow, on friday. Some of the leaves have been turning yellow. Also some have been developing orange spots. Is there is something I need change/do to stop it getting worse? Rating: 5