Mobile app issues with LTM on version 13.1.0.3

We have an application which is running fine on version 11.6 but when we migrated it to version 13.1.0.3 we are facing severe performance issues. Actually this app helps field sales experts to upload the pictures and deals through their mobile/ipad app to system. one picture clicked from ipad or iphone is approximately 1.5MB in size. When running the application on 11.6 the picture uploads time is approx 8-9 seconds and works smoothly. while on version it takes 4 minutes and 40 seconds and some times it times out too. Packet capture shows issues with tcp ZERO window.We are using very basic configuration with default tcp and http profile. No issues with ssl as we are experiencing the same issue on http as well. As it is mobile app we tries f5-tcp-mobile profile on version 13 but no luck. Anyone has any suggestions ?