you are doseing and you maybe losing some of the stuff on your rock like good worms do a water change and do not add anything else. Your rock maybe doing a cure that should not be happening. I realy don't know what it is your tank is doing but I am guessing. doing a water change will not hurt anything. I have gotton this sort of smell and it was when something died and I didn't have enough flow in the tank. Flow should not matter in the case of some thing dieing.

Bill