Austin Tx, wet spring, JM in pot, 5 yr old, in filtered light suddenly brown dry leaves. Green and dry dropping. Branches look somewhat ruffled.
Yes, your tree may very well be suffering from root rot.
Make sure the excess water is allowed to drain from the soil.
If the container is on a flat surface, you can 'lift' the container to make sure the water is draining.
Move the container to an area, if possible that rain water does not hit the tree.
Allow the container to dry out and wait and see.