Does it look like this one? If it does, get rid of it and get a new one. The newer Lumicon filters have a harder coating which will not fade like the older ones do. The older ones fade over time because they used to "sandwich" in layers.
The one in my pic was purchased used....I told the seller what I saw and he asked me to DESTROY it, so that it wouldn't circulate and nobody else would get it and use it this way!
I've heard others say that theirs still work ok this way...so you don't REALLY have to destroy it unless you have OCD like I do.....LOL