Opened up a credit card and am using less than 20% of credit, but my score dropped by a lot?

Hello all. So I thought I kind of figured out the building credit game, but apparently I’m wrong.

A couple months ago I opened a credit card with Capital One. It gave me a $10k limit, and I thought if we used 20-30% of that, it reflects really good for your score. So far I’m using about $300 of it and paying it off on time and all.

Well yesterday I got emails saying that my credit card usage went up and my available credit decreased, and my score dropped from around 780 to 726. I don’t understand what I’m doing wrong, I thought opening up more accounts was good.

Before this, the only card I had was a TJ max credit card with a $2300 credit that I used around $150 of each month, and I closed it around the same time I opened the new one. There was a month that went buy were a payment of $0.00 was due, as I was using the rest of the rewards and whatnot.

Does anyone have any advice? Is a jump in credit like this normal? I personally do not like credit cards at all and prefer using my debit mostly, the only reason I’m getting these is to build my credit. Any advice is appreciated.