so i keep treated water in 1 and 5 gallon containers to ease my water changes and i had a a 5 gallon container of water that had been sitting for about 2 weeks that i had not used yet, when i went to go use it i took the top off it smelled like old lunch meat or something, and there was white stuff floating in it looked like well i dunno. i just dont know why this would happen, could it be my water treatment stuff that could have caused it to "go bad"

if air can reach it, i dont see why it cant go bad.... stagnant water is known for getting moldy, smelly and stale. Especially if its not oxygenated...i dont think you can keep it stagnant for that long.