likely overly active bacteria.
either you add slightly too much culture, or your milk is very well ripe (which could be a sign of good cows, or if you get bad flavors could be a sign of sick cows) Or your atmosphere is affecting things.
Elevation, air pressure, humidity, and air temperature all can affect the activity of the culture.
But the most likely candidate, without any more information, would be too much culture added at the beginning. Next time, try adding a touch less starter to your cheese and see how that does.
The problem with overly fast acidification is that it tends to dry out the curd more than expected.
You need to follow temperature targets as close as possible. They are there for a reason. The bacteria grow differently under different temperature conditions. Especially with raw milk, a higher temperature may mean that you encourage different bacteria to grow than the recipe intends, or cause the same bacteria to act in different ways (producing different by-products and therefore different flavors)