overnight yellow leavez in veg.

In just 2 days my plants fan leaves have turned yelliw and completly died
shes 6weeks in veg
in ffof ive only added 1/4 strength nutes
could it be she is starving?
Should i bump up nutrients to 1/2 strength?

It could be a few things, actually. Take some photos and we can better andwer your question.

Nutes could be your problem, it was for me the first time around. Since ffof is pretty hot to begin with, you should be feeding just with water until well into veg, maybe even hold off on nutes until flowering or until your plants start showing deficiency. Pics would help.