Hi Meyer,
I am new to the world of pc (just took a course over last 6 months but that is it), but we did have a good success with a peach tree this summer that had the same issues, leaf curl, teeny fruits and teeny output. Last year I treated the yard with homeopathic silica 12x (just put a dose in a bucket and sprayed around the curled plants). This past spring we retrofitted a big sheet mulch around the tree, with soil, newspaper, some cardboard and old echinacea stalks, let it sit for about a month, then planted lupine and false indigo close to the base. It has done amazingly well, hundreds of yummy peaches. Actually too many to support, so that we had to pick many before they were ripe so the tree wouldn't fall over! Oy! If it's not one thing, it's your mother!
Sheet mulching is miraculous! I imagine adding shrooms to that would be superearthly.
. Best wishes,
Laura Whyte