Credit Score Question

So, I had credit card balance of $424, I wasn't working, so I used my stimulus check to pay it off so I didn't miss a payment.

Before paying it off my score was 734 and my new FICO score was available yesterday and it went down 15 points..

The ONLY difference from last month to this one is paying off the balance.

I have 1 inquiry from 2 years ago thats about to fall off. 1 car loan that is my fiance's, he has never been late nor missed a payment. 1 credit card with $4500 limit. No collections accounts.

Does paying off a card and having no balance make your score go down?

I'm not super smart in this department but we are about to work on getting a house and of course mine went down right before we go to get pre approved..