Hello @rohit_ja 
For your convenience, when you deploy an app anywhere and need to set CORS, you can use an environment variable called CORS_ORIGINS. In your case you can use CORS_ORIGINS=https://app.forestadmin.com (I don’t know your provider, but setting an env variable can be done either in your remote instance configuration, or using the .env file 
)
Can you test again using this variable and removing the additional middleware please ?
Keep me in touch 