'Pinched' stems/puzzling/PICS

One week into flowering and this happened overnight to one of a friend of mines plants - the stems appear pinched and then the leaf died - any comments welcome as cant find this anywhere on the site and friend worried that it is fungal. I said someone would know what it is on this site, so any comments welcome - see photos of leaves removed.

I think it is "damping off" and if i am correct then yes, it is fungal.

Friend thought this was a problem at soil level, didnt know it occured at higher levels of plants and on leaf stems - whats the solution? get the plant out of the room? has put a fan on to circulate air - any solutions welcome thanks