I don't know if this is the same, but I have some older 60+ yr old apple tree's and the past 4-5 yrs, about this time they ALL start going from green to yellow leaves, and many of the leaves then die and fall off
tree's still make good amounts of apples
but I been blaming it on a lot of excessive WET yrs and , many lat cold spells and frost!
as both have been very common since this started happening
there is about 20 tree's here doing it, some several hundred yards apart and of many varieties!
so that seemed like the best idea I had on what is happening, your maybe different,
but seems excessive water and cold spells turn my yellow and make them shed leaves way way early!