What the heck?!

So I’ve been getting dark lines on the BFP strips since Friday, but no positive yet. The top strip is yesterday morning. Then I used the first response brand last night, and got a line that I have to squint to see because it’s so light. Then the bottom strip on the top picture was from this morning. What gives?! Why am I getting dark lines on the strips, but very faint lines on the first response? Like trying to predict when I ovulate isn’t hard enough 🙄