In the VM Summary of the slow processing I only see 668 MB of used heap. Although the graph shows peaks up to 2 GB, the memory is released thereafter. So it's not a memory leak. I see also 8.096 total threads started on this VM summary (live are 44). I don't know why the started threads are stopped at all because they are pooled and should be reused.
If you want you can shoot a thread dump (kill -3) if the standby consumes again memory and cpu to see which threads are working so hard.
If we don't find out what the problem is, I suggest you submit a Gold incident
here so that we can dive into it.
