Have you heard of this?

My daughter is now nearly 7weeks old and her bellybutton isnt healing the health visitor advise me its Its a umbilical granuloma and very common yet my mum has never geard of it or her sisterand there kids.
Ive been told to salt it for 20 30 minutes twice a day it doesnt seem to be healing but its common th8ng apparently ive got 3 kids my mums had 4 and my mums sisters had kid's too and not one has had this before