I have some left over bottles of distilled water from when I last filled and flushed my system 6 months ago. Both are open with the cap on, and have about a half gallon of water left together. Are they most likely contaminated and not ideal for a flush?
Already put about 6 gallons through and I still get some red dye coming out.
if the caps have been on then it should be fine for flushing.
Yes
Yes should be good to go. Distillation removes impurities of the lids have been on then those impurities aunt have returned. One small thing they have been opened and used so if they had been stored in sunlight bugs will grow in it but then you would see green growth or 'bits' in the water sounds like you have managed to avoid that.