Premature graying...? (21)

So I’m 21 but I’ve been dying/bleaching my hair for the past 2 years. Like 5 months ago I stopped everything and am growing out my natural hair. Well now all of the sudden I’m noticing I have gray hair!! Like 5 just on the top front part of my hair and my mother in law found at least two in the back while braiding my hair. I still haven’t made an actual effort to see how many I have. Anyone else have an experience with this? How fast does it go from having a few to it being noticeable?