You never said which version of the game you're rocking, dude. People report getting low FPS on the new ULTRA MEGA SUPER BROKEN test build that is the "new" 0.9b.
My best guess is hardware issue. I'm not sure if it's related but the lights inside the base used to lag the fuck out of my game until I upgraded my GPU.
My "best" solution for this problem is to use glowsticks instead of the base lights. It won't solve the problem completely but it should make the game playable.