I don't get why you people ignore experienced growers and take advice from people who have no idea what they are talking about. Purple has nothing to do with nitrogen def. that is pure stupidity. Purple is genetic variable not a deficency.
To be honest there are tons of reasons why this could be happening. I
highly doubt this case is the result of temperature, and is probably indicative
to nutrients.
By the way what do you mean pure stupidity? In my opinion giving advise
that the purple is a “genetic variable”, when you don’t have a clue what the
genetics of this plant are is a lackadaisical answer. Giving precarious
solutions doesn't make you sound like much of a “experienced grower”. To me it
sounds like you may be one to take the easy way out and deal with little potency
and small yields.
“To each his own.”