Just to update (sorry for extremely protracted delay!)
Left front tire was becoming trash - the belt(*) within a few more days got so separated that the tread looked like an "*" (I should post pics - unbelievable)
I in the meantime had checked Discount Tire'* website and analyzed the codes on the tires, which revealed to me I had two (Chinese) tires 10 years old and two (Brazilian) tires that were 13 years old... One of the Chinese ones was the culprit...
(and all these tires were of a manufacturer we all recognize as "American")
What threw me was they all were really decent as far as tread and not being dry rotted (having those cracks in the rubber - dryrot? agerot?)
Anyway, bought 4 new matching tires and all is good (actually really good - better handling, ride, etc)...
So much thanks for all your input and help!