I had the same when I was pregnant with my second. She was really active one day and then 2 or 3 days she’s go really quiet. I’d get checked out because you can’t be too careful. Every time it happened to me I got checked out
I used to out the remote control on my tummy when I was pregnant with my 17 month old, I couldn’t feel the kicks but could see him moving x
Have ypu been moving arpund a lot? I generally don't feel my baby kick as much if I've been active but if you've noticed a decline in kicks go either call your midwife or go to triage better to be safe than sorry