Dayton fan running slow...HELP!!

Not sure if anyone can help but rep to anyone who can help. I have a 235 cfm dayton squirrel fan hooked to a elf can off a 10 ft run. The problem started last week when I hooked up a valuefan to cool my hood. I live in a doublewide home so I had to mount both fans underneath. The dayton is on it's second grow and has been working great but when I had to move it to make room for other fan the speed dropped. I have them mounted on the steel tongue under my place. Had to move the dayton about a foot and that night noticed the room wasn't getting cool like it did. Went underneath house and redld the duct work and tried a couple of different outlets but nothing helped. The fan is about 4 years old but just started using it last year and now it is giving me problems and with the warm temps on the way!
Do these things need oiling I thought they were self lubricating? I am out of ideas. Hope someone has some. Thanks

Thanks!!!!!!!!!!!