My fermentation appears to be stuck. Expected FG is 1.014 or lower. Its been 1.019 for eighteen hours. Can I add some Allinson's Easy Bake yeast? There was only one packet of yeast in the kit but the 'best before' date is Feb 2021. It's only three days in and I'm happy to wait. The 'wort' was about 25C when I added the yeast. The krausen was about two inches at one stage, judging by the 'tide mark'.