Equisweet Sucralose Aspartame Free

I have been purchasing Huletts Equisweet Sucralose Aspartame Free since 2011 and the last two boxes of 100 do not sweeten my tea or coffee but leaves a bitter taste in my mouth. The first box was thrown away but the second one is still with me. Expiry date is 22/10/2017. Have you changed your product or is there a problem? We tested the new box with a box previously purchased and the difference is obvious. If the product has been changed please advise so that I can source an alternative. Regards Cornelia Tiley