To update this thread: Turns out I was right. Paying off the AU account to zero was the cause of my score dropping 15 pts.
New DPs: Allowed AU account to report $36 and when EX updated overnight, I regained 16 pts. Oddly, the "No Recent Installment Loan" negative reason, what we thought had triggered it, has disappeared. I do not have any new loans. (just the old paid and closed Affirm loan)
Account balances as of today:
Cap1 AU: 36/18,000
Barclays: 259/4000
TD/Samsung charge card: 0/3200
Sync Amazon Store: 0/3500
Other changes this month but were already affecting my score: Barclays balance went down a little. AAoA reached 1yr6mo. A new INQ from Citi on Sat (new card not reporting yet), but saw the -3pts on Sunday. So, all changes in the last 30ish days: 761 - 746 from AU account reporting zero; +4 to 750 when AAoA upped a little; No change when Barclays balance was reduced; -3 pts to 747 for Citi INQ; +16 pts to 763 when AU account reported new balance.
