4 Banks rate me at 815 credit score. NASA gives me a 783. I wouldn't worry. Did you get your free credit report for the year just to make sure there are no errors?
Answers

If you did, and that type of credit is now a closed account, that can cause your score to drop.

I think the third bullet below is what lowered my score.
Regardless of the FICO® Score version, the keys to obtaining favorable FICO Scores remain the same:
- Make payments on time
- Keep credit card balances low
- Open new credit accounts only when needed

https://www.myfico.com/credit-education/whats-in-your-credit-score
"Your FICO Scores take into account:
- How long your credit accounts have been established, including the age of your oldest account, the age of your newest account and an average age of all your accounts
- How long specific credit accounts have been established
- How long it has been since you used certain accounts"
so not only was the third of your bullets a factor, but likely you shortened the average age of your credit accounts by both closing an older account and by opening a new account(s)..
For example: if you had 3 cards ages 30, 20, and 10 years, your average age of credit was 20 years, if you closed the 20 and added a couple zeros (new cards), you now have 30, 10, 0 , 0 for an average age of credit of 10 years.

Maybe you should get a report from Trans Union

I note, Discover indicates the score is based on TransUnion data. So perhaps TransUnion has some error about you, you might want to check your TransUnion data. Maybe there has been some identity theft. The different credit scoring places can get different data, they do not always all get the same.

I closed an active Amex cc account that I had since 2001 and opened another new one with them. In doing so, I lost that lengthy credit history doing that. I also added another new cc from Chase and still kept the old one active. Opening new accounts, or closing old active accounts takes a toll on the credit score since the score is partly based on the length of the credit history.

I also in the last 8 months Gotten
a Chase Freedom card and a Citibank Extra cash back card with bounuses. My scores went down about 5 points.