Did you remove the coil or did you just clean the top of it? I'd hate to rewick when the rayon looks nice and white and the flavor is still good.
That's the thing with rayon. Your coil cocoons up with YUK long before the rayon poops out then once you remove the rayon from the coil rinse it off its barely browned and looks like it can be used again. I don't see why a good rinse then scraping off the chunkies the best you can too get a bit more life out of the build. Depending on the circumstances and atty its prolly easier just to toss the entire build then have a wicked spare handy to install than to remove, rinse, scrape, maybe loosening the wicking then reinstall but in a pinch if the wick isn't burnt then rinse, scrape, blot the excess water then refill should do.
Cotton turns dark and burnt looking from the juice flowing inside the fiber getting crusty then plugging up the fibers one at a time until it starts to dryhit.