Shiny Eevee evolution

I’m trying to get every evolution of Eevee in shiny form. However, I’ve gotten 6 Jolteons in a row trying to get flareon and vaporeon. I only have 2 shinies left to evolve. I know everyone says it’s random, but why am I ONLY getting Jolteons. I’ve done it over 3 days already.. please help!