EXCLUSIVE

Prog-rockers Coheed and Cambria just earned a crap-load of karma ... after saving one of their die-hard fans from losing her home.

Cyndi Crouch -- who helps run a C&C website -- setup a GoFundMe page asking for $3,500 to help with her mortgage payments ... and the "Welcome Home" singers instantly pledged $3k.

Guitar player Travis Stever says they did it because "she's a really awesome fan who is extra proactive and supports the band in everything we do."