flush the medium with twice the volume of water to the size of the container. (if using a 2 gallon container flush with 4 gallons of water) make sure the water you flush with is between ph 5.5 and 6.5. I add h202 solution to all my waterings and flushes. if it doesnt help, then you will at least be able to give it a better diagnosis and have a fresh palate to start with.