why are my plants turning purple?

I’m about to weeks from harvest and most of my leaves have turned dark purple and it happened after my heat went down to around 60-65 at night. So I’m thinking phosphorus deficiency. What harm will this deficiency do to my plant? How can I correct or should I do anything at all?What are the symptoms if you have to much phosphorus?

Yeah I was wondering that too my plants I have two plants in the same pot and only one of them turning purple