Spider mites tend to affect the growing buds of the tree. *If you had a big infestation, it might also impact the older growth.
Try flicking a branch over a sheet of white paper and if you get little dots, try smearing them with a fingertip. *Red streaks=spider mites.
Looking at the tree though, I would still suspect a watering problem.
The brown growth is unlikely to return to green. *You can prune it away. *An
JR-1163 Ashinaga or a
JR-0164 Azalea shear is great for thinning juniper foliage. *I would recomment the 0164 if you have small hands.
Please review the section on watering in the ***FAQ*** there is also additional info at **LINKS*** under Techniques->Watering. *Juniper can withstand a lot of sun. *The soil should drain well and not remain soggy. *You should rewater before the soil dries out, but before it has dried out. *A piece of chopstick pushed into the soil can make a convenient "dipstick" to tell you when the interior of the soil medium is beginning to dry.
Regards,
Matt