Conifers seeing red
Yes, it could be spider mite damage on your conifers or it could be aphid damage. There is a species of aphid that attacks conifers causing browning also. If it is spider mite you will most likely see lots of webbing in the branches. Treatment for either pest is quite difficult as the sprays to use against these pests are normally contact based and it is difficult to treat large trees or hedges with these type of products. There are biological controls using predators that can also be used but it is getting a bit late in the year for these to be used outdoors now. If the trees are small and you can get good access to them, I would suggest spraying with Savona Fatty Acid available from Harrod Horticultural. This kills pests on contact but you need good coverage with concentrate spray when diluted. Repeat every 7 days for 2-3 applications. If this is not practical then you may need to treat with a systemic insecticide available from garden centers, which are not organic and for that reason, are not available from Harrod. I hope this helps.