Preheat the grill to medium heat. Lightly oil the grates.
Cut each avocado half into 6 slices and cut the peach into 8 slices. Arrange on a cutting board or baking sheet. Lightly coat both sides of the avocado and peach slices with olive oil cooking spray and drizzle a little of the lime juice over the avocado.
Place the avocado and peach slices on the grill. Cook just until grill marks appear, about 2 minutes per side. Remove from the grill.
Once the fruit is cool enough to handle, roughly chop and transfer to a bowl. Gently mix with the remaining lime juice, jalapeno pepper, salt and cilantro.
Turn the grill to high heat. Lightly oil the grates.
Place the fillets on a baking sheet or cutting board. Lightly spray both sides with olive oil spray.
In a bowl, stir together the paprika, chili powder, cumin, thyme, salt, garlic powder and olive oil until a paste forms.
Rub the spice paste all over the mahi mahi fillets.
Place the fillets on the oiled grill. Cook for 2 minutes, then flip and cook until the fish is just cooked through, 1 to 2 more minutes.