Yes, those three leaf springs keep the chassis suspended. They will sag a bit with time and you need may need to tighten them to lift the chassis to the proper height.
To get access to the rear spring, remove the non-moving rear part of the lid (not the lid itself!). Two screws near the top corners when looking at the rear panel of the deck.
Don't lift the chassis too much, or it will start scraping on the top. The top surface of the platter should be 2.5-3 millimeters higher than the surface of the deck, with no record on and the arm carriage pushed to the middle (careful with it!).
Each spring has two screws, you need to figure out which one is for height adjustment and leave the other one alone. By loosening the other one, you can turn the springs around so that the platter is exactly in the middle of the opening horizontally.