line progression?

R. 🍃 • 👩‍❤️‍👨👧🏻🤰🏻
Hi ladies.
I got a positive test yesterday. 
And i took one this morning. 
Top is 3:20 yesterday afternoon. 
Bottom is 7:20 this morning. 
Why is yesterday afternoons test darker then this mornings.
Should i be worried?