It's weird Lexort- to me they look so overwatered- the purple stems, the way they're yellowing a bit the way plants do when they can't get enough N because roots are too wet. They do look a bit off-color, and the stems are very purple. Purple stems aren't something to worry about much necessarily on their own and can also just be genetic. It does seem like something else is going on with your plants though. I know we've said this all before... There are lots of new growers who freak out when they're stems turn color like this- and that should be disregarded. However, there are also some experienced growers who claim that purple is a sign they need feeding.
This is what Jorge Cervantes says about purple stems.
This is what Jorge Cervantes says about purple stems.
Cannabis stems turn purple for various reasons. Cold temperatures, below 10 degrees C. cause the supply of phosphorus to diminish, which in turn causes leaf stems and later main stems to turn purple. However, they also turn purple when phosphorus is in short supply due to a toxic (fertilizer) salt buildup in the soil. Nitrogen deficiency can also cause leaf stems to discolor.