You could be overtraining, yes. You improve outside the gym when you recover from what you did in the gym.
The problem with your setup is that you are more than likely overtraining your shoulders and triceps as they are involved in the same movements as eachother and chest movements as well.
Another problem is that you're devoted far too much time to upper body and neglecting your legs, and you arent doing nearly enough pulling work.
This is the folly of bodypart splits - you double up on some things and leave other stuff out.
The better way to set things up is in terms of upper or lower body movements, and whether those movements are a push or a pull, in the horizontal or vertical planes of movement.
So a bench press is an upper body horizontal push, where pullups are an upper body vertical pull, and deadlifts are a lower pull and squats are a lower push.
This is far more efficient, as this way of thinking lends itself to the inclusion of bigger compound movements rather than single-joint isolation movements, plus you dont have to be in the gym every day.
My advice would be to read the stickied topics at the top of the training forum and put together a program using that info. Its hard to get your head around at first, but it honestly makes more sense this way, and youll see better results for sure.
Welcome to IM.