Welcome to AFN spliffy. From my perspective, I see nothing wrong with reusing coco or peat mediums so long as you don't sow directly to them. You will probably want to "wash" the used medium by running a few gallons of weak nutrient solution through it. That should pull out any residual salts that may have been left behind from the previous grow. I grow organic mostly using coco in my base and reuse my soil with every grow. That being said, I always sow in fresh peat and transplant after the plant is about 6" tall. There are a few growers here that use H & G with good results. No reason you can't use them in coco. Best of luck buddy!