Is the reason Sollux talked with a lisp that he had 2x as many teeth as normal, which is why his lisp went away when he fell down the stairs and got them knocked out?
Probably, having messed up teeth can cause a lii2p
Probably, having messed up teeth can cause a lii2p
There are others
Vriska killed them to feed her lusus. Eridan may have been involved since he used to Flarp too but Feferi most likely not involved.