Ask a vague question get a vague answer. This is how I'd trouble shoot the following scenario.
All connections to a FTP server seem to be downloading at an abnormal slow speed. This is an internal FTP server, being access by internal client.
Connect to the device that the server connects to. Check the port config of the port that the FTP server connects to. Confirm there is no speed duplex issue or port errors, if it's clean check utilization This includes the FTP servers NIC config. I can't count the number of time a client device(this includes servers) is set to auto and my switch port is hard set at 100FD and there's a negotiation mismatch. Once the client device is hard set, the problem goes away.
hope this helps