The tap water here is pretty good and really soft (not sure about trace minerals though), so I don't use any kind of filtration or water conditioners. I haven't noticed any fermentation issues in the past, and the only yeast nutrient I have is diammonium phosphate, which I assume doesn't include other trace nutrients. I did attempt to make a gluten-free golden strong a while back using sorghum extract from my HB store and sugar that turned out really "cidery". Though I've attributed it to not pitching enough healthy yeast or (less likely) something with the sorghum syrup. This time around I have a 1 gallon glass jug to make an even larger starter, so hopefully that will help.