Could you tell me what types of conifers these are?

Hello, I believe these are Emerald Green Arborvitaes. 

Kirk - there could be several reasons why your arborvitaes are turning browning (it appears from the bottom up).  Check the soil around the base of the trees and if dry or compacted, the lower branches will die first as the little water or nutrients available feed the top of the tree.  Or possibly, they are just showing signs of stress from winter burn where strong winds affected the vascular system during cold weather this last winter.  

Also, these trees may have an insect problem like spider mites which suck the nutrients out of the tree.   Other potential issues are detailed in the link below.  If there is no evidence of insects or disease (which you should see), then we are back to winter burn or water issues.

https://henderson.ces.ncsu.edu/2021/11/plant-health-alert-arborvitae-problems/

Unfortunately, if you prune out the brown growth, new growth will not sprout from the woody area.  I suggest before you get to the cutting down stage, that it would be worth the fee to call in a licensed arborist to assess the health of the trees and possible remedies.  You can find a licensed arborist in your are through the website below.  Hope that helps.

https://www.treesaregood.org/findanarborist