Lower heart rate


So at my appt today I had expressed that my little one has been moving today. The doctor used the doppler and her heart rate was in the 120's which is strange because it's usually in the 130-140 range. She said she'd like to do an nst but their machine was being used and said if her movements don't pick up today to head to triage. Am I right to be a bit worried? Her movements have been a lot softer too and she's usually an extremely active baby.