So you are still hitting all the pH markers?
winter milk has more solids in general. usually, fat goes up more than casein protein, but it depends on the breed and feed. If you are making no adjustments to the process even though the milk is different, consider it. Generally, for winter milk, you can get away with waiting less time before cutting curd, and you may need to use more starter.
Can you get your milk solids analyzed and post them? A Lacticheck or milk lab can give them to you.