I brew with just a ready made beer kit and sugar (combination of dextrose, maltodextrin, and malt). Recently I have started adding hops that are sealed in a kind of tea bag. I put them into the brew just after the fermentation frenzy has died down but not stopped. Usually 3 days. Is this a good idea or do I risk contaminating the brew. And am I compromising the bitterness, the taste or the aroma of the hops. Any advice?