Leaky mag pump - How would you repair it?

[I am using a Mag 2 pump for recirculation on my calcium reactor, and it looks like there is a leak that I need to repair. It looks like it's coming from the face that you can screw off and on. Could it be the thin rubber washer being worn down? Any suggestions on how to get the leak stopped?]
 
[I think you could remove the screws, add some silicon grease on the o-ring and replace the cover. Be sure to tighten the screws evenly. you could also get a replacement o-ring.]
 
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