What are some things that cause a weird, lighter period?

I’ve been getting periods for 14 years that have always been fairly consistent (besides teenage years).

This month I thought I was late by a couple days.. but was early by a couple days (after ignoring the app that got dates wrong) and my period is SO much lighter than normal. Like usually I bleed a ton and this time it’s barely anything. It’s much lighter in color as well *pic below*.

What are things that can cause such a shift? I mean, I am ALWAYS the same in terms of how heavy my cycle is and at what points in it

. Yesterday and today should have been my heaviest days as they were 1 & 2 and it looks more like it’s on the way to being over!

(Photo for color reference)