Mild Discoloration - First Grow

Well, SWIM's had this discorloration for a while, but its getting more and more noticable so SWIM's getting worried. Ive looked at the stickies and cant really narrow it down exactly...

The larger plants are about 3.5 weeks old and the smaller are abouta week and a half. Grown indoor with a 70W MH lamp and a couple handmedown CFLs. A new 400W lamp is on it's way, and with that investment SWIM doesnt want these plants to be unhealthy.

SWIM's using some kind of Miracle Gro knock off thats pretty low in NPK, however SWIM's using is a 20-14-13 orchid food (Better Gro).

The plants are growing pretty slow, which i suspect is due to the 300W light shortage, so if anyone has any comments or tips regarding things other than the discoloration please feel free to speak!

Thanks for the help, Im glad to be a part of this community and i hope to be the one diagnosing other's problems in the future!

your new light will help tremendously! they dont look like they are getting enough light right now. As far as your leaf color, looks like a very mild nitrogen deficiency. I would only give them a small amount of nutrients now though, you really dont need much until they are over a foot. To be safe you should leave it and wait to see if the problem gets worse. Looks good so far!