building your cake correctly is important.
with only a 5um filter in there, you are almost certainly getting media in your flask. throw a 1um filter paper on the disk, and then build the cake correctly.
see: CRC taste like shit change my mind - #594 by cyclopath
be sure to follow the link to @TheLostBiologist’s tek.
its not about “washing” the media, it’s about running the fines back through the bed so it “sets” correctly and will filter finer.