Sour/Vinegar Tasting Cider

I made some cider on 5/8 using non-preservative juice and three cans of non-preservative apple juice concentrate. I used Wyeast 3068 and an adequate amount of yeast nutrient blend. Over the past few days the fermentation has become slightly cloudy and now has a distinct "vinegar" or "sour" taste that is not super strong but definately present. This flavor was never there before but some how I feel that it was simply covered up by the sweetness that has now been fermented away. Just wondering if anyone has ever experienced this and if the sour taste is natural and dissapates with aging. I don't think I have an infection but who knows. Later!

The natural acid in cider is malic acid. To get a feel for what it tastes like buy some "sours" candy, its a sour tasting acid which is used for a food acid in candy and the like.
if this is the flavour it's natural, you can get rid of it by doing a malo-lactic fermantation, or wait for the flavours to balance better with age. If it is vinegar it will have a distinctive odour and you may see an acetobacter 'bloom' on the surface. This will only happen if o2 gets in.
Generally the advice is to relax and wait.