Have the same wash down pump and never had it leak. Is this something new or happen since the original install?
I'm sure you've done this already, but remove the fitting and inspect, re-install making certain it is clipped in properly. Also possibly check the fitting to see if there is a small crack, etc. (possibly from over tightening the hose clamp). If you do put lube on the seal/o-ring use a silicone or non-petroleum lube.
Another thing to check is the hose connection. Is the hose clamp on correctly or the hose split or small hole from the hose clamp (try to isolate/identify the leak location)?
if fairly good and if this leak happened during the install, maybe its a defective hose fitting.