Strange smell from fermenting Coopers Cerveza

Hi Guys.
On with my 3rd brew which is a Coopers Cerveza.
It's been in the fermenter 3 days and it has has a decent Krausen so it all looked good til I went in the boiler room where the fermenter is and got a rather strong whiff. Not a pleasant one either. I can only liken it too an item of food which has gone off.
It appears to be from the fermenter and smells very 'gassy'.
Do any of you reckon this is an infection despite it appearing to be fermenting?
Everything was carefully sanitised and the kit and brew enhancer were in date.
But puzzled as my first two brews were great.
Thanks guys!

Different yeast and different recipes can give different smells. Some fermenters smell TERRIBLE... like sulfur and death. Google "rhino farts", for example.

Remember that fermentation is, at its core, a decomposition process... so an "off" smell is not a bad indicator.

Relax. Odds are everything is perffectly fine.

Yeah,some lager yeasts can def be described as rhino farts. I always thought dino,but you get the point. It does age out though.