need hydro help -- attn: Guru's!

Hi,
I recently purchased on of the EZ Hydro Kits(the one W/ the 125watt Saturn
dual spectrum bulb) for 160.00 off of ebay. It came with everything needed to
start growing. So I did.
Anyway, my problem came at 2 weeks and 2 days since planting. The new
leaves that are forming have some yellow in them. Could it be that I started
them on nutrients too soon? I followed the instructions that came with the
kit. 2 weeks of 5.5ph water only. Then turn the pumps on with nutrient solution at 2 weeks. Solution has grow, base, and catalyst in it.
Well, I have given as much info as I can think of. What is my problem and
how do I fix it????? Help is much appriciated.
Thanks,
redbud :confused: