Opks not getting darker??

Bailey • Lucky wife 💍 Fur momma to five 🐶🐱🐱🐱🐱 Angel momma to three 👼👼👼

The app says I’m supposed to ovulate in 2 days, but my opks aren’t getting darker at all. Am I doing something wrong?? Bottom pic is last three days. My cycle is an average of 35 days.