Black scale and fireblight, over 95 degree weather, cultivating too close to their shallow root systems.

Did you raise them from seed or did you buy them and put them in the ground 5 years ago? Describe the dying leaf condition. If you bought these trees already started were they grafted types?

Did you check for ground voles? I've lost dozens of perennials, many shrubs, tall palmettos, pindo palms, and european fan palms to them. I no longer water anything that's established. Spot watering during droughts really seems to attract them.

Why are you watering every day?

Keep mulching everything..the voles love it. Predators can't find them.

this is the time of year(back to school) when you can find all sorts and shapes of metal mesh trashcans. They are wonderful for planting in areas that have voles.
Cut out some hardware cloth and after planting, wire the hardware cloth around the plant and connect it to the trashcan mesh.
Get as wide cans as you can find so your plant will have room to grow a strong root system.
Also good for plants and perennials that you want to dig up to store for the winter. If you leave 2-3" of the top of the trashcan it's easier to pull out of the ground.

If you do have ground voles, they're loving the tasty damp roots and multiplying like (meadow) mice. Stomp the ground around the base of the affected trees - if it has vole tunnels the ground will feel spongy. I apply a mix of hot sauce suspended in dishwash liquid and water. It will deter them, but you must remain vigilante. If your loquats are mulched, get rid of the mulch asap. Metal mesh trash cans is a great idea, or you can plant them in large plastic containers with the bottoms cut out and replaced with a 2' layer of crushed gravel