Silver mica disease

[Jonathan]

After getting fed up with the FM sound on my Zenith 7H822Z (Z denotes tone control), I decided to take apart the discriminator IF transformer apart for inspection of silver mica disease. The FM sounds distorted, as when I tune in a station to it's maximum level, the audio is completely distorted, and only sounds good when tuned to low levels. AM section only works (works pretty decently when the antenna is connected). When the antenna isn't connected I get no stations and a 60Hz buzz. With FM, my audio level is quiet and I get a 60Hz buzz, and distorted audio is heard over the 60Hz buss when a station is tuned.

Anyway, I took it a part and noticd the silver mica sheet is discolored arount the edges. This a bad thing? The mica looks fine, but I want to add discrete mica caps anyway, because the discolored around the edges doesn't look right.
Is this a sign of silver mica disease? And what cap values should "I use for the discriminator IF?

Thanks.

Jonathan