Beginner Gardening: HELP!!!!!!!my cacti are turning into cardbord, 0 by cactibobo

cactibobo wrote:
desarster i came home from school and the Cereus the one with big thorns had fell over and got almost snapped half way down and at the top half the top has broken off complaetly
also the gray stuff on the Cereus is hard but it is not affecting the juicy bits inside as there is a smallish hole where the grey stuff is i can see the green wartery stuff and it only is on the skin also the top is very wet witch sugests the grey stuff isent doing any harm
what do i do about the brakeges
many thanks cactibobo