Yes, you need to get the humidity up above 70% if you can. You can do this just by placing a cover over the jiffy's. If you don't have a cover for the propagator you can make individual ones from plastic bottles or clear plastic cups.
I also recommend using a spray bottle on those seedlings to keep the seed casings moist and make sure they fall off - nothing worse than when the seed case gets stuck and kills the plant. They're tricky when you have to pull them off as the plants are so delicate at this stage, so make sure you keep them moist until they fall off naturally! If you do have to pull any off, use tweezers and be super careful.