My last batch was a stout and it blew the lid off the fermenter. I cleaned the led didn't think much of it. When it came time to bottle, the gravity was a little higher then I had expected but after having checked several days in a row , it wasn't dropping. I bottled it and have let it be for about a month. Now I've noticed that some of the caps seem slightly poped up and when I open the bottles the head gushes up the neck of the bottle. I'm pretty sure this is a bad thing. Can some one confirm that this is bad and tell me the cause.