The purpling on the stems may be from the strain. I have some purps that have the purple leaf stems. From the same batch of seeds two other plants have all purple stems.
And as for cold turning the plant purple, the leaves get lightly purple at first and gradually darker as it gets colder at night, kinda spotty. I dont think 53 degrees should be turning the leaves purple. I had 44 this morning, and they are definately slowly going purple.

Your buds look great .....