If you're seeing yellowing of the lower sets of leaves and burnt crispy edges with the purple stems it's a mag deficiency from my experience when trying to find out what is happening with your plant try to notice everything lol detail and write a list of the things that you're noticing on a plant instead of trying to identify the issue with just 1 symptom it helps to notice every lil thing with your plant in order to properly diagnose your plants issue last thing you want to do is ask it helps if you can figure out the issue on your own with reading everything you possibly can related to this plant understanding why plants do what they do and how and when they do it is a good starting point once u understand the basics things will fall into place gracefully....good luck man...