I have a few different varieties of Island Mist Kit wines that’s been in the bottle now for 18 months ago or so and they seem to have lost their flavor and turning a little sour. Do these sweet wines need to be drank by the year mark?? I make them per instructions and add a 4 pound bag of sugar to them to up the gravity some. Just wondering if it’s me or are they just that way. Thank You for any responses and your time.