You will sometimes see a drop from paid baddies, and yes, as stated above it's mostly due to AAoA. However the removal of the baddies will aid in the cleanliness of your CR and will allow it to grow.
I'm pretty sure it was his AAoA that caused this based on the info he provided. It looks like when the 2 accounts fell off he lost 1.5yrs on his AAoA.
Sound about right?
There's not enough info to calculate AAoA. I didn't see the mention that AAoA remained the same. I think his 1.5 yr mention had more to do with the most recent baddie vs. the age of an acct.
I would suggest to OP though to recalulate AAoA. At the least it was approx. a 6 yr acct if AAoA is at 6. I'm guessing OP looked at a FICO report to get the AAoA? OP, is that right? If so, AAoA is accurate, but you can still lose if it is among the oldest accounts reporting, oldest revolving, oldest installment, etc. because the length of history within each classification would have diminished (assuming it is older).
Also, OP, I got to thinking. Where are you getting your score from? I assume one is a lender. Is the newest from the lender too? If not, where is it from? That can explain the score difference. Also, if from here, was it TU or EQ? If from TU then that can explain the difference too because of the FICO version used.