SQL Server - Log file not shrinking in AlwaysOn group

We have three-node AO group in SQL Server. Primary node, one secondary node in Sync mode and another secondary node in Async mode.

Main Database on Primary node, log file-size is 434GB, Used 99.91%. Log backups is happening every hour only on Primary node.

Ran following query on Primary and Secondary servers.
SELECT log_reuse_wait_desc
FROM sys.databases
WHERE name = 'Main DB Name'

Primary node
log_reuse_wait_desc
------------------------------------------------------------
AVAILABILITY_REPLICA

Secondary-1 node (Sync mode)
log_reuse_wait_desc
------------------------------------------------------------
LOG_BACKUP

Secondary-2 node (Async mode)
log_reuse_wait_desc
------------------------------------------------------------
AVAILABILITY_REPLICA

While other DBs (much smaller than main DB) in AO groups log usage is very minimum (1 to 10%) and can be shrunk,...