Nite burn or deficiency?

Plants 5 weeks into flower older leaves yellowing with burnt tips. New growth looks fine. Could this be mag def or did I just overfeed? Wouldn't the new growth be crispy if it was nute burn?

Edit damn autocorrect can't edit title

Older fan leaves will die off durring flower. If new growth is ok your fine.

The new growth is taking the nutes form the bottom leaves that don't really need it i normally just trim them off after 1/3 of the leaf looks yellow. Only on the bottom fan leaves that are not going to produce anything.

looks like phosphorus def to me

Yeah it looks like that but if it is just the lower fan leaves most likely just the buds and upper canopy taking the Phos. from the lower leaves that are not getting the light really needed to help the bud grow. A pic of the whole plant would be better to see if the new growth is having same problems.