The issue was resolve by altering the 2 values in the php-fpm setting as mentioned below:

catch_workers_output = yes
decorate_workers_output = no

Thanks to the below 2 post :

1. https://symfony.com/blog/logging-in-symfony-and-the-cloud
2. https://dev.to/mtk3d/how-to-configure-php-logs-for-docker-2384

After updating the above settings in "php-fpm.c/www.conf" file, we were able to get the debug logs.