I'm not a expert by no means but that mix your using might be a little hot . Did you use any plain soil at the top of that mix . I heard of people using seed starter mix or just plan promix at the top of a mixture like. I def would hold on the nutes for a while with that mix. But I would ded raise the ph 6.8 then check it again. Could be that that mix is a little hot. But don't freak out. Mine finaly started to work out and are doing good . How's the growth?