Are you in an area that encountered lower than usual temperatures this winter or early spring? This tree shouldn't be fully hardy in USDA Z8, I wouldn't be able to grow it here.

"Orchid trees do best in acidic soil and suffer under limey conditions.
Moisture: Water freely during the summer and less so in winter. Orchid tree may drop its leaves during winter drought.
Hardiness: USDA Zones 9 - 11. Orchid tree is a subtropical plant that usually recovers from brief freezes (after dropping its leaves)."

Hi, it sure sounds like too much water. I am in Houston and the leaves only barely fall after blooming and seeding. Then it gets new leaves and fills out. Yellow leaves either means too much water or too little water. In your case since green moss has appeared, there has probably been too much water.
When leaves fell from mine in the spring, I asked about it. They fall at this time of year.
You didn't mention how big your tree is. Mine is about 20 to 25 feet. The most wonderful tree. I water only when the no rain for a while.
It has been an easy tree to take care of.
I would leave the tree alone, but gradually let it dry out. It would seem that too quick drying out would be too quick for the tree. Hope this helps, Carol in Houston

grdn4fun, one of these trees and I believe that it is variegata, flowers in the early part of the year when the tree is leafless. Another, purpurea, flowers towards the end of the year while the tree is in leaf. The two species are difficult to tell apart. There are a few other spp. which have different flowering habits and characteristics.

I have a similar problem, except that the leaves have brown spots and have started to fall really quickly.

serg started his own post ....