AotS DLC for founders

I am confused as to why the DLC in steam won't unlock. I bought AotS aaages ago as a founder and only just decided to install it and play it. I am a bit confused, the steam key unlocked the base game and the 'Overlord' dlc.., but nothing else. I was under the impression the founders edition came with all future dlc? Have I just misinterpreted something way back, or is this a legitimate problem?