Why has Rufty got tufts?

[Ruftysdad]

Rufty is an elderly horse who has Cushings. It is well controlled and he has never had any symptoms apart from being ribby. His coat has always been normal. However this year when he shed his winter coat he had developed lighter tufts all over. He did have fleas just as he changed his coat. These were treated by the vet and he has been clear for a couple of months.
Anyone any idea what has triggered this.
Tried to download photo but said file too big

 

[Rumtytum]

Can’t answer sorry, but if you’re using an iPhone then take a screenshot of your photo, crop the edges if you want, then upload it (much smaller file).
Good luck with your question?