The two older ones will definitely be fine (so long as they were fine before, of course). The one you just brewed may be affected by the higher temperature. It all depends on how much it had fermented by the time the heat went up.
When the yeast are digesting sugar at higher temperature, they will produce more esters, phenols, and higher alcohols - in most styles of beer, excessive amounts of these are considered off-flavors. The amount produced will be a function of how high the temp was (quite high, in this case) and how much sugar is digested at that temp. If your stout had been, say, 90% fermented by the time the temp went up it should be little affected. If it were half done, you would probably have pretty noticeable off-flavors, though how much depends on the strain of yeast, etc, etc.
Even if it had a ways to go yet, fermentation probably had already passed the crucial lag phase and the first 12 hours or so of fermentation, which are most crucial for flavor profile. And yeast can clean up a lot of off-flavors they produce given time.
It's too soon to despair. Perhaps it will not be quite so good as it might have. But I'll wager it'll still be at least fine, if not better. Barring problems other than elevated temperature.