I've done a little bit of research and it says that it's normal that the traps turn brown after eating, but the plant is way too small to eat something visible to the eye.
Also they don't look very green to me as they were before.
Yeah, too much water. Too much soil that holds too much water for way too long. Bummer!
I would get a mature sized plant from a nursery first. Learn how to feed insects to it...not too much !! I love where it takes two taps for the plant to FEEL secure that the insect is worth catching.
Always always use potting soil for any plant in a pot, terrarium, planter. Always. Cheapest is the bestus. No fertilizer added and no water holding gimmicks added! You need to be in charge of fertilizer.
Venus fly traps also rely on photosynthesis for energy. Did you put rocks or gravel beneath that soil? That would also account for the 'bog'...