yes, the connections would have timed out. But the pool will assume that they are still used by the application and hence do not have a way to re-cycle them or validate them.
If you enable connection-leak-tracing that might give some clues. If there was connection leak, stack trace of the caller that acquired the connection with appropriate message (as shown in the above blog) will be logged.
If you do not see any log message, it is possible that the issue is due to in-sufficent pool size. There is more load in the system such that they cannot be served with the current connection pool configuration (max-pool-size).
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