|You should have your own internal DNS server to handle lan traffic name resolution.|
What OS is running on these two servers?
You have too many switches off switches. There should be no hubs.
proper topology design is as follows;
Server room contains the servers and a backbone switch [managed gigabit switch] with enough ports to support server growth and network expansion.
Each floor should all be wired to one location and that location has one switch with enough ports to support expansion.
Each floor switch is connected to the main backbone switch.
It is recommended you use the same switch on each floor except the backbone switch as well as purchase a spare which you can quickly swap out in case of switch failure.
You should not have pcs connected to switches that are acting as uplinks. This puts the pc traffic in conflict with all the other pcs that are connecting via the uplink.
Presently you have 11 switches uplinked to each other. The above recommendation reduces this to 4 with only uplinks to the backbone switch.
If for what ever reason you can't change the switches then wire them all to the main switch in the server room not each other.