@HeavenOhioMy first guess is that something aged and that either your AoYA (age of youngest account), AoOA (age of oldest account), or AAoA (average age of accounts) were positively affected.
I don't believe that any of those factors would have changed over the weekend (18th-19th) as age of accounts factors all increase on the 1st of the month with them all growing in age by 1 month at that time. If today was the 2nd or 3rd of the month I would definitely say that this would be the most likely reason.
OM is correct that it could be due to an inquiry becoming 365 days old, as they become unscoreable at exactly that time with the date of the month being a non-factor.
OP, it's important to understand that there's no such thing as getting a 4-9 point "bump" (or loss) for "no reason." There's always a reason. The FICO algorithm only considers data when generating a score. If you're seeing a different score, it can only be due to different data. You'd have to go through your two credit reports (before/after score change) account by account, line by line to determine what could have caused the change. The most common reason for an insignificant change such as the one you referenced IMO would be something utilization-related. Perhaps number/percentage of accounts with a balance dropped, a balance on an account dropped, or something along those lines.
