Provinces Lost to Allies

I think its all about morale, when you have low morale and not enough soldiers on it, then you have a chance of revolt

Thanks, I definitely have a food shortage and 2 of the provinces had food which makes it even worse! Thanks for the response.

Yes it is all about morale. Also food for thought for later on in game if you have a recruiting office and if it is making units for you the units health points are based off that provinces moral. Example (if i am at 50% moral the the unit that is recruited will also have 50% health). This is a reason you would want to keep your moral up so you can have a stronger army.