I haven't worked with Citrix ADC but if it's like any other load balancer you want to look at the SNI configurations settings and the TCP profile/buffer size. I

I haven't worked with Citrix ADC but if it's like any other load balancer you want to look at the SNI configurations settings and the TCP profile/buffer size. Increasing the buffer size may help but from my experience if you are offloading SSL then the buffer window shouldn't matter since the HTTPS connection is not being decrypted at the destination but who knows maybe ADC requires a larger buffer for HTTPS versus HTTP.