new seedling problems

[treeshaker]

HELP i planted tomato and pepper seeds feb.13 in jiffy pots with jiffy seed starting mix. put them in the jiffy greenhouse on a heat mat with grow light set for 16 hrs a day. they came up really quick, but now they are getting yellow leaves, the plant is real thin and purple colored. this am i mixed up a VERY weak solution of miracle grow fertz. and put some on the plants. it has been so long since i planted seeds i don't know if this is normal or not. soon as them plants reached the top of the greenhouse i took it off and unplugged the heat mat.

thanks guys and gals