Cabbage unusual color

A couple of my cabbages developed some purple/maroon leaves after it frosted two nights in a row. Up until then, the weather had been pretty warm. Google leads you right towards phosphorus deficiency but could this be a case where the cold weather just affected the plant from being able to take up phosphorus for a couple of days?

My soil is new and I added extra granular fertilizer before planting, just doesn’t seem like the soil itself would be deficient in anything yet. The cabbage has been in that pot for right at a month. Thanks for any help!