Slowness on Server 5.5 with Dual G5 Tower

Here is our setup:

We have 3 G5 towers running 10.3 with 1 gig of ram, and 1 G4 with 10.3 running our FileMaker 5.5 servers. We have about 250 databases spread accross the 4 servers. Our network address scheme is 192.168.0.0 / 255.255.0.0. (aka multiple subnets to broadcast accross)

Here is the problem:

Users report slowness throughout the day, even when the servers are not doing a backup. Common problems are:

-long time to perform finds

-clicking buttons that run scripts and getting the Mac OS "spinning wheel"

-just browsing through records

-entering in fields and tabbing accross to the next field

In addition, sometimes it can take several minutes to view the list of all hosts when trying to get into a database.

Has anyone else experiences similar problems, or has a suggested solution?

Some things we have throught of are:

1. recovering all files

2. defraging the servers

3. checking to repair permissions on the disk

4. changing the subnet mask from 255.255.0.0 to 255.255.248.0 to make the network smaller

Will any of those help? Any other suggestions?

Thanks in Advance