Very common for older speakers with foam surrounds. A number of places sell refoam kits. I don't think you even need to remove them from the cabinet to refoam them. There used to be a site in southern California that repaired drivers and sold repair kits, but it looks like they are shutting down. Parts Express offers various services:
www.partsexpress.com and they have people who can likely instruct you on the process for refoaming the drivers.