I had two more of the litre bottles left of the Mr. Beer brew I did and decided to just drink them. I took them out of the closet and the bottles were soft. NOTHING like the other that were rock hard. I put them in the fridge for a few days and still nothing so I opened one. Flat as the day it went in the bottle. No fizz sound when opened and no carbonation at all. What would have caused this? I mixed the corn sugar in boiling water and then in the beer.