Issues with purple stem and yellow leaves in Autos starting at the bottom of the plant and moving it's way up the plant ?

This website ( https://www.growweedeasy.com/cannabis-symptoms-pictures ) covers many common diseases and nutrient problems. I don't think they cover the purple stem but yellow leaves can be caused by a few different things.

Maybe start a diary with your equipment and lighting your using but good grows take good equipment and good nutes and environment without any good environment and equipment its not worth the electric cost especially in uk happy growing but the plants are only good if temperature is good enough and lighting is strong enough