Need Help Seedling are very purple

My girls are about 2 weeks old in solo cups. There in a mix of ffof and coast of maine organic soil. They were all growing good except slight discoloration on Big Bud. I looked at them to today and the bottom of the leaves are all purple please lmk what i should do. temps have been pretty stable above 70 but RH has been pretty low in the 30-40s.

Try and get your temp steady around 80f or 27Celsius 70 is a little chilly fir the girls this early in the grow. It's nothing to worry about though. It's a pigmentation cause by anthocyanins which is what gives berries their colour.