The answer to your original question is: Yes, that is plug fouling and what you did was the correct first actions, which worked. If that had not wrked you need to be familiar with the recommended actions for your engine. Usually there is an RPM to set and the mixture is leaned to an approved setting. This normally works, otherwise you may have a problem with the mags. Remember, this is the very reason you do the check so well done on being thorough!!