When you migrate to the new instance was it to the same kind of instance or to a different size?
It seems the bottleneck is php-fpm:
[22-Oct-2019 13:04:08] WARNING: [pool wordpress] server reached pm.max_children setting (5), consider raising it
Can you try increasing the value of the
pm.max_children setting in the file
/opt/bitnami/php/etc/common-dynamic.conf? Please restart the servers after making the change:
sudo /opt/bitnami/ctlscript.sh restart
According to this test, the TTFB (Time To First Byte) of your site is almost 18 seconds. Try to run another test in https://www.webpagetest.org after changing the php-fpm to see if it helps.