What's causing this?

I have two winesap apple trees that have been planted approx six years and are approx 12 ft tall. For the past several yrs the trees have had plentiful blooms but the fruit doesn’t mature and fall off. This year the same thing happened again except a few have managed to hang on. Is this a bug problem, or fungus problem, fertilization concern? I am in zone 7b.Any help or suggestions would be greatly appreciated.

On some of those fruits I definitely see quince rust - the little orange pricks sticking out. It is a disease. The standard spray is myclobutanil (Immunox) at petal fall. For this year it looks like you are too late, I would pick off all the infected fruits to try to break the disease cycle. Read up on cedar apple and quince rust to learn how the disease alternates - if you have juniper trees nearby that can be removed you may also reduce the incidence of the disease.