Building on @JuiceBox 's comment -- Are you using rubber bands at all on the lift? If not, then that's probably reason #1 that your motors are having to work so hard. I've never built a 6-bar, so I'm not exactly sure where the rubber bands should go (perhaps another commenter can tell you), but I recommend watching some youtube videos of robots with 6-bars and seeing what those teams are doing for placement. Use YouTube's slo-mo on some reveal videos to see details. The rubber bands should be enough that you can manually move the lift to the middle of its height and let go, and the lift will just stay there on its own.
Building on what @RuizK1 said: One way to reduce friction is to use VEX high-strength gears with the round green idler inserts. See this other article I wrote about Idler Gears & Inserts . (I sound like a broken record on the Forum lately; I have indeed written many articles.) However, swapping out gears is rather time-consuming, so that may not help you for this weekend.