looks like mould forming on the surface of my banana fruit vinegar......

i finished a batch of banana flower fps not too long ago and decided to use the remains to make vinegar. I replaced and equal part of rain water as the amount of fpj serum extracted. the solids at the top that are actually slightly obove the liquids are forming what looks to be mold at the 2 week marker. did i add enough water? could the rain water have been contaminated?