You have likely overtightened your Berkey PF-4™ Fluoride and Arsenic Reduction Elements. You have likely damaged the screen on the inside of the element and the elements will need to be replaced. This will cause the media from the element to leech into the lower chamber. Don't worry, it is completely harmless.
This is not covered under the Limited Warranty. Please contact your local Authorized Berkey® Dealer to purchase a new pair of elements.