Im going to assume this is just a windows file system agent without DCE. The first thing i would check is, if software compression is turned on for this subclient. If it is, turn it off and see if things improve. If it doesnt or if its not on, then check if signature generation for dedup is turned on the client. If its is, either move signature generation to the media agent or turn it off temporarily to see if the situation improves. Both of these options are on the properties of the subclient under the storage device tab. Since you mentioned you have mulitple subclients, ensure you perform these steps on each one.