My grapes yeast doesn't bubble as much as should be on 5 th day. Few bubles, less sound of bubble production as if it has stopped it's activity. But the grapes have changed colour.What is the problem? I had put the har in hot water. May be my grapes were not of quality. Some were soft , broken,is this the reason my yeast is inactive? Please reply me,I am a beginner.I love cooking and to make my own yeast.