When was the last time or how many miles since a new filter & fluid went in?
It is a good idea to do this every 50 k miles.
Dexron VI (6) is what you want to add or use when servicing transmission. There are no problems adding to a trans with another Dexron fluid.
The Dex 6 should have less aeration as well. Do you have one or two bubbles or lots? What additives did you add again?
I also have 4t65e and keep it slightly above full line when hot, after 30 minutes of driving, otherwise it seems to hesitate going into drive or reverse sometimes when cold.
If you are planning to do a trans service with new filter etc, now would be the time to consider adding a a half or full bottle of Sea Foam Trans Tune.
This will safely clean the valve body & solenoid by removing any varnish type build ups. I noticed improved shifting soon after using the Sea foam.
Trans Tune - Sea Foam Sales Company