The availability of milk for cheese production is lower than expected.

Even though in the overall number the remittance of milk from farms to industry increased 3.4% yearly in the first 3 months of the year, it can be explained by better outcomes from only 2 major companies. If those are taken out of the equation, then production would have shown a decrease.
Given this situation, there is not that much milk available for cheese production and producers are not having a surplus to offer. They are trying to comply with current customers.