I wouldn't think the tannins would be affecting your cycling. The only true way to know the status of your cycling is to have all of your 3 major readings. You have the ammonia, but you still need the nitrite and nitrate. Without those everything is speculation, and with the ups and downs you are unfortunately going through, speculation doesn't help any. This is why some people (myself included) don't like the idea of fish cycling. It just makes things harder on you. I would suggest pulling the fish so you don't have to worry about harming them, and using bacteria starter. Have patience, and don't give up!!!