Ceramic Coated Woofers

Does anyone know something about the Ceramic Coated Woofers that are in the Avalon Symbol and the Studio Pro.
Mine have a brown discolor near the rubber and on the rubber there seems to be a oil like fluid.
All 4 woofers of mine Studio Pro`s have it.
Have send several email to Avalon , but they never respond so I hope someone on Audiogon can give me a answer.
Thanks.