Those junipers look very healthy to me in general. The denseness of the foliage suggests it's a some Chinese Juniper cultivar. Dense foliage is great for bonsai, but it can also attract spider mites and fungal issues if they don't get good air flow. Makes sure your junipers are getting lots of fresh air and (outdoor) sunlight. If you think it's got some pests, try a general pesticide first and/or a fungicide reccomended for conifers. I've heard some pros reccomend Mancozeb (fungicide) for junipers. Neem oil is not generally recommended for junipers because the oil can cause foliage burns in warm weather. Good luck with your trees!