Concerned about condition of roots

[Miyuki]

I don't think the problem is with water between the leaves, as all is well from the new roots up. I'm not at home to measure or take pics, but my best guess is that the plant is 24" from the older roots and about 20" from the new roots it produced this summer. I think there is about 4" from the new roots to the lowest leaves. Only the older roots seem to be a problem, and they only feel slimy right after watering. Otherwise they are firm, so I don't think there is rot, but I'm not sure. If it is time to cut off roots, how? and when? is best to go about this. If it is best to try cleaning them off, how should this be done? Swamper, how did you do it?