FYI - Higher octane gas than recommended by the OEM will actually cause harder starting with your equipment. Higher octane fuel by it's very nature is harder to combust and thus the less chance for preignition and detonation.
I'm betting your problems are carb related and oil related. Disassemble the carb and clean with some carb cleaner. Then reassemble and dump out your old fuel. Put in some new fuel with a 2 cycle oil that is manufacturered by one of the OEM's, not something you just purchase off the shelf.