The brown mask that you described is normal with a TCA peel, along with the tight feeling. Everyone responds differently to the peel. Some have a lot of swelling while others do not. Usually the swelling goes down within a couple of days and you can apply a cool compress if needed, which may help bring the swelling down.
Your skin should start to peel between days 3 and 5, and can take up to 7 to 10 days to finish peeling. Once it starts to peel the tightness you are feeling will get better and the brown mask you described will come off. The skin underneath may still be pink and tender, so be careful and gentle with your skin and wear sunscreen everyday. Good luck and enjoy your smooth and glowing skin!