I have a situation where i have Merge pull subscription using web synchronization. My replicaiton was working fine but one fine day it started getting slow and it is showing lot of pending changes to be synced.

I did notice that my download changes to subscriptions are working fine in quick fashion where as my upload changes takes lot of time die to which all the subscribers are stuck with lot of pending changes. I checked index fragmentation and missing indexes and all are upto date. Kindly help me debug this issue.