My old pitty got also bald patches when he was younger ! After the vet check them under the microscope he can see that was Demodex ,a type of mibes ! After few weeks putting some spezial stuff for that on it , it goes away and than only the fur has to grow there again ! till than it never break out again !
the vet tell me , every dog got demodex , it could break out through a low imunesystem , maybe a sickness or something ! On a healthy dog it don´t break out !
at that time he was a little sick due to bad weather ! You write she is on diet , if she is a little fatty maybe that could be the