Are you using the same brand of tests to test? Also with first pee? Really the only way to confirm HCG is lowering is through blood tests. You may be fine though, may just be the hook effect or might just be slightly more hydrated.
I wasn’t testing daily but when I got the first faint days after a strong positive I realized my pregnancy symptoms were gone. Later that day I wiped it was pink and the bleeding started the next day. Hopefully it isn’t a chemical for you. If you can get blood tests you should! And pay attention to your pregnancy symptoms.
What kind of test is this ?