Help- 4w5d and BBT DROPPING!!

Heather • baby boy #2 due Aug 2019!

Asking for my sister who is around 4w 5d pregnant. Her first HCG scan was 25,000 yesterday and progesterone was 29. She will repeat HCG tomorrow.

Her temps have been dropping over the last few days. Should she be worried? No cramping or bleeding:

Thx for your help!