If it's not enabled you have to set static IPs on everything that connects to it. (And sometimes that isn't even an option--I've seen small electronics with Wi-Fi capability but no ability to set an IP.)

If it's getting slower and slower there must be something wrong. In the old days I would suggest something like Wireshark and see if there's junk on the wire but these days packets normally only go where they are supposed to, making it very hard to sniff out problems.