thats to low at a ft tall u should be at 600 ppm. start with 300 ppm for the fist week of veg.add 100 ppm per week if starting from seed at the end of 2 months u will be at 800-1000 ppm wich is ideal......to me it looks like u have a magnesium deff.look at the fringe around your leaves.u could have this elemet locked out do to ph issues.