where are the spots coming from?

I have a 2 yo qh filly. She's always been dark bay. A few months ago I noticed a few white hairs along her topline. Over the last few months they have developed into white spots of hair. On top of that there are single white hairs popping up all over her.

She's never had any sores or anything there where the hair would grow back white so im confuzzled lol

Here are a couple of pics

That is strange! It almost looks like the white hairs are forming a pattern. Do you blanket her?

She gets rugged during winter but we are just coming out of summer. She hasnt been rugged for about 6 months at the moment

Thats strange, I was going to say maybe your saddle doesnt fit her, but it doesnt look like saddle marks to me...

Lol impossible to be saddle marks as she isnt broken in yet :) has never even had a saddle on her back YET. Been driving here lately so saddle is coming soon but not yet

I noticed today the spots are starting to spread to her butt. But why lol I don't understand this spotty anomaly :S

Maybe she's part appy lol
That's really werid though

Maybe she's roaning out in a weird way lol

Could be that, how old is she and have you seen her parents, my gelding changed color for a long time until he reached chocolate colored bay. I've had him since he was 5 mnths., and I really hope that my wife's filly stays blue (pictured below)

Looks like lacing to me. Very cool : )

Like this but not as extreme:

Wow, it almost looks like the start of reverse brindle, that's really interesting! I would love to know the color of her parents, etc...