Dropping apples is more a function of what crop size the tree can support and growing conditions.  If a tree has too many apples it will drop some in June to keep the tree able to support the rest to maturity. And then there are trees that produce lighter crops every other year.  Many orchard owners will hand thin fruit in June/July to produce larger apples and prevent fruit drop later.

Without a picture of the current status of the Snow Sweet I can’t accurately say what the cause is.  Compare what you are seeing with the following websites.
1. https://bygl.osu.edu/node/2002
2.  https://extension.umn.edu/fruit/growing-apples