For the color change, have you compared parameters between the 2 tanks? and have you compared the amount of lighting?
If you have them in cups, it should be pretty easy to increase the amount of light, by standing the pots on rocks or something, to get them closer to the light itself.
If you have them in cups, it should be pretty easy to increase the amount of light, by standing the pots on rocks or something, to get them closer to the light itself.