Hi, sorry for the newbie question, I'm sure it's been discussed a million times but have new brewer anxiety with this one! I'm bottled my second brew, first one was perfect. Second is a mangrove jack Bourbon Barrel and after doing exactly the same(check SG, wait, sterilise bottles, carbonation drops x2 in 500ml bottle etc etc. Just opened two peta bottles admittedly after only 6 days and they're flat as a pancake. Any advice would be really appreciated as it tastes amazing.. but flat!