Could be either but, given how healthy it looks I'm with @Grand Daddy Black in that it's probably genetic.not sure I've seen the main stalk an branches this red before, I've had stems on leaves like that. could it be genitcs? or maybe a deficiency? the plant looks healthy and seem to be growing fine
But, cool temps negatively affect the plants ability to uptake P which can also bring out the purples and reds. Some growers do that intentionally for the pretty colors but, since it's brought about by deficiencies, I've never seen the point of deliberately inducing problems in a grow that could negatively affect yields.
You've had some cooler temps recently so it will be interesting to see if it greens up as temperatures increase.