i'm afraid there's nothing you can do.
most importantly, don't take it your responsibility to "make them more happy". i know that you love them, and i think you are a good kid.
but they are adults. they have their personality, their experiences and their own choices. don't try to imagine that you know better than they are or that you can decide something for them. they have to sort out their own problems.
otherwise you would start having personality problem yourself and you'll ruin your own life later.
and so are you. you have to take care of yourself and your own problems, because sometiimes they might be too occupied with their problems that they cannot or forget to take care of yours.
if you can take care of yourself, your studies, your social life and everything, you can take a large trunk off their back and they can concentrate on their own problems.
having said that, i dont mean that you should not talk to them when they are calmer. tell them how you feel.
sorry about the whole thing.