Early period on pill

I have been on the pill since May, and I switched to a lower dose of my birth control last month (I’m mid way through the second pack). Last month there wasn’t a change at all, but this month I am bleeding a week earlier than my period is supposed to come. It’s more spotting than anything. It’s brown with a little bit of red blood.

Is it because I changed the dose? I’m also extremely stressed right now.. what could this be from?