GMSgrowsanswered grow question 4 years ago Red stems on leaves and stalks in veg cycle can be shortage of nutrients. That doesn't mean you just add more it means you check your runoff water and make sure your ph and ec levels are where they should be. Ph off or ec to high can cause elements to become unavailable to your plant. Reddening/purplish stems is usually a sign, of under nutrients., if it isnt genetic related. Cheers