Dark Green Leaves and Purple Stems

Dark lush green leaves is normally a sign to to much Nitrogen, this can also be influenced by extra Magnesium in the soil. Purple is sometimes a reaction to the LED lights, it can also be a sign of early Magnesium deficiency or some other stressors. It can also be genetic as some plants are purple. Looks at the stains page your growing if its from a common breeder on the site and see if any other plants were purple. take note it could be a phenotype as well as not all of them may purple up.