HELP! Leaves turning dark purple!

So I'm 23 days into flower and I recently noticed leaves on the mid/lower part of the plants are turning dark purple and some yellow. From what I've read it seams like it could be a nitrogen deficiency. Is it too early in flower to be seeing a nitrogen deficiency? We had some cold temps last week but the temp never went below 50 in the tent at night.

50 is pretty low and its likely that caused the purpling and maybe the yellowing if everything else is in check. I never let my room get below 60 prefer 65...except last week of flowering if i really want my buds to color up. If you are going from 80 to 50 this can shock em a lil bit and also increases chances of powdery mildew with a 30 degree swing. 15 degree swing seems to be optimal.

Did you feed flowering nutes or veg nutes in the first two weeks of 12/12? Some strains will yellow early if nit given veg nutes during the stretch period.

50s are too cold The purpling is a normal response to the low nite temps.

I fed them flower nutes the first two weeks of 12/12. I'm about to feed them tonight, should I do half veg nutes and half flower?

At 3 weeks in a bit of N isnt going to hurt.

Plants don't look that bad. Some strains have naturally purple leaves. Maybe these are those.