Confused on test progression

I had a chemical or mc in June. I got a positive frer on Sunday. I was between 11 and 13 dpo. My beta was only 28 two days after my bfp. Today I took an frer and the line is lighter. It got me really scared. I peed

in a cup about 30 mins later and used 3 more tests. I got a yes+ on an frer, and got darker lines on a top care brand and easy@home test. Is it possible that the one frer was a fluke? Has this happened to anyone else? I'm thinking it's another chemical but really holding hope.