Q.Pineapple Guava Tree / Feijoa
I had 3 trees and my other 2 died the same way as the last one is turning. This one grew big within 6 month and it started drying out. Nothing changed with watering. It just starts drying and the dirt is not too wet and not too dry. I live in Central Florida, not much heat recently.
Certified GKH Gardening Expert
It sounds like an infection has taken over the soil! This can cause many trees and plants to fail when planted in this area.
I would recommend using a fungicide to help kill off the infection. You may even consider solarizing the soil.
These articles will help: