Why is one positive darker than the other?

🥰❤Mother of 1🧒🏽😍 TTC #2

Lastnight on CD20 I got a positive opk and tonight I took another to see if it was still positive and this time the test line was even darker..why is that? Glow says I ovulate between CD20-22

Also should my temp be dropping or rising since I have positives?

Tonight's test cd21

Lastnight cd20