Are they getting darker?

Terra • Married to my Mr. Right. Mom to my IVF heart warrior daughter born November 16, 2017.
So I am on cd 14 of my second cycle taking letrozole cds 3-7. Last month I didn't use opks but I def ovulated as my cd 21 progesterone blood work came back at 51.2 which was great. I'm guessing last month I ovulated around cd 16. This month would more then likely be the same, just unsure if these are getting darker towards to bottom?