Perhaps I should switch my question and be more specific...
What did they do to reach 1800 regularly when they were at my rating around 1600
Switch my openings and start killing people
Yeah that was basically it... Was facing a lot of 1700+ and 1800+ players at 1600, arenas helped a lot.
First off, to improve at blitz, you need to improve at slow play. Your blitz strength will follow. So start by playing some slower games. And not just the amount of time on the clock. Actually use that time. Slow down and think more, and you'll see things more deeply than when you play blitz. Once you get used to looking more deeply, it'll become instinctive, and you'll do it fast enough to think more deeply in blitz, also.
Second, nobody can tell you specifically what to study without looking at your games. You need to review your own games honestly, especially the losses, and look for trends. Maybe look at your last 10 losses, and try to figure out what they have in common. Are you getting bad positions out of the opening? Are you doing ok in the opening, but then blundering tactically in the middle game? Are you avoiding tactical blunders, but just not finding good plans in the middle game? Are you reaching endgames that you don't know how to play and losing at that point? Are you just playing too slow for blitz and timing out regularly? Whatever it is, that's what you need to study and improve.