Hasn't happened yet to me in my playthrough, but I am the host and no one else in my party is using those skills. Maybe try respecing in the mirror and getting those skills again? Not sure it'll do the trick but hard save just incase, since getting those books will cost a bit.
Maybe a mod conflict if using. If on steam (idk about gog), try verifying game cache/files (maybe whole party should try it that too, just incase).
