all yellow leaves --> harvest?

A friend just called and said on one of his plants all of the leaves have turned yellow and droopy. We talked last week (leaves on bottom of his plants were yellowing and droopy) and I suggested he increase N a little and maybe a Mg Tx. That didn't happen and things got a lot worse with one plant, all the leaves are yellow. He is prob 8wks into flwer with a long flowering sativa, should he go ahead and harvest? Should he flush first or just cut it before something else goes bad? Thanks in advance.

that's tough... pics would help a lot.

u should check root bound
my first 2 grow had droppy yellow leaf in flowering why ?
cause i didnt have enough soil
and plants stop growing
died
and i smoked some dead buds
wasnt good..