Measuring Small & Surprise Twins.. Maybe

I am, by my calculations, 9 weeks 4 days. Last week I had my 8 week Appt and the fetus measured 6 weeks with no heartbeat. Went back today for another ultrasound and there are now 2 fetuses, but the one that was seen last week is still measuring the same with no heartbeat. The fetus that was not seen last week is measuring the same as the other now. HcG levels today are 71,000. I go back in a week for another ultrasound and bloodwork. Does anyone else have an experience with this? I’m trying not to be too negative or too hopeful, but I am SO confused.