Stupid question about first response

Cherish

I’ve been getting positives since 10/11 DPO and I had some extra FR tests so I’ve been using those to check progression along side pregmate. My last FR test I had was a rapid results and I used it today the day of my expected period and it’s positive for sure but it’s lighter than my FRER I took yesterday. Is this because the RR is less sensitive? I’m not really worried just curious. The pregmate test is definitely darker than the one from yesterday