Please help...

My daughter took a home preg test in the afternoon and got a faint pos. The next morning she took another 3 (2 different brands), all positive. That same afternoon she had slight bleeding the next day she went to hospital when it didnt stop, they took bloods and said her hcg level was 3 (not pregnant). I understand the levels would reduce in the event of a MC. But with the tests only picking up levels from 25 and above to go down to 3 by the next day i thought that was very fast. Is there a chance the bloods could be wrong?