my canary is loosing feathers

by kamel
(lebanon)

hi, dear madam/sir
i hope you can answer my question, i have a canary( female) and a male, for more than one year, about a year ago, the female started to lose feather , 1st the tail than the chestand the neck,than the head, it is almost like abold eagle , the only part that is still left is the wings(also not fully covered, and some on the back), i thought it was a a disease but the male is still healthy( not contaminated), and if it was a disease, shouldn't killed it till know
i appreciate ur answer.
best regards. have a nice day.