Lowering HCG at different lab?

Hi all! So last Wednesday I went to the ER because I was having some deep pressure on only my left side. I thought that was a little suspect so I went into make sure it wasn’t an ectopic pregnancy. According to the app last Wednesday I was suppose to be around 8 weeks. Anyway, I went in and they did ultrasounds and blood work to double check everything. Ultrasound was fine but they said I was measuring in at 6w3d and they couldn’t hear a heart beat which i heard can be normal. Then they said my hcg was 24000 and to have more blood work done on Friday to make sure it was doubling. I did go into get blood work but at a separate lab 2 days from then. I called the OBGYN to see what my hcg levels were and they’re now at 17000. The PA asked if I was having any bleeding or spotting and I don’t. Not even a hint of blood. Has anyone else experienced this with different labs? I’m going back to the same lab as Friday to get my blood work done and I have an ultrasound this Thursday. Just wanting to know if this has happened to anyone else and their results.