Lowryder Yellowing - What could be the cause?

[foxysox]

I have a couple lowryders that are about 3 weeks into growth that are experiencing yellow leaves. .....?.

Yellowing leaves... first thing you should think of is N deficiency. And at 3 weeks yeah, that's about right if....

I once used very very dilute grow nutes as per highbreds instructions,?.

...if you have only ferted them once, and dilute at that.

I used a epsom salt foliar spray last night so I am hoping that may help. ?.

Epsom only cures Mg problems

Does anybody think I need a flush?.

No that would make it worse. You need to give real fertlizer with a high N value.