Overheats in slow traffic, am running out of ideas, thought it was water pump.

Thank you, I accidentally used the wrong coolant for two or three days. Car no longer overheated but since I used the wrong coolant it’s leaking coolant right above the thermostat, looks like the back of water pump. I think the green coolant caused the waterpump seal to fail a little. It’s a small leak, and the waterpump is less than 6 month old just changed it. I drained and flushed the cooling system and got rid of the green( made for older fords) to blue for Subaru within two or three days of putting wrong coolant. And I have changed waterpump thermostat radiator, and fans, with a fan shroud ( which stoped the overheating. At first it was a bad fan, then 12 instead of 14 inch fans. without the shroud it did not cool the coolant down enough. Has not overheated since I put the fans with fan shroud on. But now it has a small coolant leak. I was thinking of using a good aluminum radiator stop leak, to see if it helps, but a friend of mine said I should not use the stop leak? Any advise