ok, after reading Dom's site...he says:
*The kefir must be shaken 1 - 2 times daily. The reason is to prevent Yeasts and Acetobacter colonies from forming on the surface of the kefir. If not agitated, these colonies may be seen as a light-brown wavy film. This phenomenon is similar to The Flowers of Wine [Mycodermia] in wine-making. In this case, I refer to this film as Flowers of Kefir [please see this picture]. Although the initial development of such colonies are not harmful, if left unchecked, unwanted molds may possibly propagate on the colonies; agitation prevents this, possibly due to increasing freely available oxygen, which I find is most favourable.
Funny, I said it shouldn't smell like acetone, and he says acetobacter colonies can form and 36 hours was a long ferment, especially if left 'alone' and not agitated.
I would just discard that batch, since you are not gonna drink it, no matter if it IS ok. I would fast them with filtered water, and since you say you have a 'small batch' of grains, use less milk (so more of the good stuff can colonize FASTER) until they 'grow up' and can turn a normal 'portion' of milk into Kefir.
He also says it should smell more like 'yeast bread' or beer, NOT like what you said. I have noticed if I leave my sourdough starter too long, it gets a REALLY strong, acrid smell to it, probably more 'acetobacter colonies', harmless but makes your eyes water a bit...hahah
SO, without being there, and having the extensive experience of the 'Dom'....I would say you have active fellas, just need to let them water fast and then give them a bit less milk to 'turn' at first.