Well, I know a little about Meyers; and your Meyer does appear to be underfed. Meyers are heavy producers and heavy feeders; they need an NPK ratio of 3-1-2 (I use 18-6-12 for my commercial trees) plus Magnesium, Calcium, Iron, and Zinc. Depending on the pH of your soil/water, you may have to give it chelated iron.

Greasy spot fungus is most commonly caused by poor orchard floor sanitation.

It looks like there could be a few different issues there. Have you done any soil tests? It's hard to say how much of what you should add without knowing what is in there already and knowing what the soil structure is. You can do a simple settlement test to determine structure. The chemical analysis is really cheap from UMass.

how to determine soil structure

The top layer (6+ inches) & supplemented when planting is ~70% sand & ~30% organic. Fine ground/degraded wood chips & sand mix.
Lower layer is ~70% sand, 20% clay, & 10% limestones or shells.