Impossible to say at this point. Metallic flavors can be caused by a variety of things - water, yeast, contamination, hops, exposure to metals, or even a combination of things.
Yeast, in particular, can throw off a number of odd/off flavors in reaction to stress.
Also note that the term "spring water" is meaningless unless you know the mineral concentrations, alkalinity, etc. Maybe the water has a high iron content. If the water is low in alkalinity, a stout using a lot of dark malts can result in a ph that's too low. Did you check your mash PH?
In short, you need to first worry about consistently brewing a clean beer. Then you can concentrate on tweaking flavors, style points, etc.
Brewing beer is a process of many variables. The quality of the beer is determined by how many of those variables the brewer can control, and how closely he can control them.
Michael
BJCP National
I guess the one thing I'm still hung up on is the "metallic" flavor. I use stainless steel brew kettles and spring water. The MoreBeer guide says that metallic flavors come from using iron/aluminum or bad water. Shouldn't be the case here. Do I attribute this to the infection too?