FTP routing in UNIX network.

Have two SCO OpenServer servers. One is 5.0.4 and the other is 5.0.5.

Both are on the same subnet 100.x.x.x/24.
FTP clients from the 100.x.x.x/24 subnet can ftp to both servers with good performance.
FTP clients from an alternate subnet 10.x.x.x/24 can ftp to both servers, but performance is poor to the new 5.0.5 server. Why and how can I fix it?