It's drowning, being watered much too often (it should almost dry out between times) and the soil should not be soil, but mostly grit (see the Soil subforum on www.bonsaisite.com for more). Also, you shouldn't be spraying it - it's a waste of time for even tropicals, and pointless on a juniper which normally likes dry conditions in any case. And why is it getting sun through a screen? It's native to the hot (in summer) and dry conditions of the west, and can take a lot of cold in winter as well. Cactus soil is not appropriate, though probably slightly better than peaty potting soil. If more of the tree is brown and brittle than otherwise, it's probably been dead a long time.