I will take the advice into consideration.

I do find it hard to believe that a daily driven car- used for several lapping days- never really more than 20 minute sessions for me- would need extra cooling.
The deposits do happen early in the sessions, so I am ruling out overheating.

Monday I will be at Mosport and will do more testing.

 

One thing that I hadn't thought about, I was reminded watching the bed in video (is it here or elsewhere) that does show how a cold racing pad can "un-bed" its material that was previously on the rotor surface. I'd consider your early session laps to be the bed-in time adding material to the rotor surface. Or just make sure you do a VERY GOOD bed-in and then take it easy to the track. If your rotors have cleaned themselves off when biting 'cold' and having friction braking instead of adhesion braking, that might help explain some of that oddness you're experiencing.

 

where could you purchase one of those rotor adaptors that allow for cooling ducts?

 

AMS had a kit with caliper brackets, ducts, etc. Not sure if they still have it.