yeah, it kind of looks like that is the problem.Im thinking phosphorus
Sounds about right. Im growing mataro blue and you can really see the bule hue with low tempsWe are no experts, but if you are 6 weeks into flower that looks like normal discoloring to us. Looks like hints of purple in there too. Could be some cooler temps bringing the purple tint out. Some times it is some sort of nutrient deficiency or environmental stress, but again to us it does not look serious.
Great looking budz by the way! What is the strain and how much longer do they need to flower out for?