Welcome to the wonderful world of Serissa. Even experts have trouble with them. I would say that, if it's looking poorly already, that will be worth doing. Moving it outside (if you're in the northern hemisphere) might help, but it's doubtful. Once they start to fail, they fail completely, quickly, even in expert hands. Don't feel too badly about it, it happens to the best of us with this genus. I would suggest an easier species for your next foray into the bonsai world, perhaps a Ficus spp.