I'm sorry and know you are disappointed. I'm not knowledgeable to offer any worthwhile opinion, but I'm wondering about the soil. It looks like they have been planted in a construction zone. Has the area been sitting without water for a long period? Also wondering if the blooms should have been removed so the plants' energy could be directed towards setting down roots. Did the plants look healthy when you bought them?

@socks: Yes, the trees looked healthy when we bought them. They are planted in our backyard. The backyard soil has a lot of stones/rocks since we purchased the property, and it looks like a construction site. I was told by the nursery that native soil is sufficient for planting avocado, as they have sensitive root system and don't like compost and manure. I told the nursery the soil in my backyard has a lot of stone and the quality is poor, but they told me it's fine, and not to water the trees often. When we were planting the trees, we filtered away the rocks/stones, so the soil was like thin powder form. Since I haven't been watering the young trees much, the leaves started to fall off. The nursery told me that it's lacking of water, so I started to irrigate more often. Then, the new leaves, buds, and branches are starting to die back. I contacted them again today, and they said the tree has root rot now, and the most I can do at this point is to reduce the irrigation amount and keep my finger crossed. I did research online, and i'm not sure if it's really root rot or not. If it is, I doubt the trees can survive without taking any treatment.

Get rid of the fruit. That tree needs to spend its energy on growing.

Also, did you dig the hole at least twice as wide as the bucket?

60 days is not uncommon for a tree to get over transplant stress.

I see this is a cross post. I thought I gave an answer.