My guess is it's Winter burn.

NY had a terrible winter this year, that may be the reason for your Winter burn....

Your thuja's should recover nicely all by themselves. They are just starting to push out new growth and will shed the brown needles all by themselves. If you want to administer a little first aid, you can give them a little hollytone to help them along. The browning is a result of wind and dehydration due to the severe winter. As the spring and summer progresses, you can do a little selective pruning by clipping off the tips that are brown - no major haircut needed. In 4-6 weeks they should be as good as new. Some of my arborvitaes are far worse than yours....good luck.

a plant that has been 10 years in the ground.. shouldnt need any fert ... especially if anywhere near a fertilized lawn ...

that said ... hollytone is rather benign in terms of formula ... and a little of this or that wont hurt ... but its not worth spending money on it.. if you dont have it laying around.. IMHO ....

ken

Wisconsin has many evergreen trees and shrubs with brown tips, brown branches, and brown leaves. You can see this while walking through our neighborhood in Madison, or driving along the interstate. It was a long winter, with many days in succession that were below normal temperature. However, there is another issue for trees and shrubs, and that is low rainfall during the previous 24 months. We did not have a severe drought here, but it seems that low rainfall, combined with sustained cold weather, has been rough on the evergreens in our state. We have an older arbor vitae in our yard, about 30 feet tall, that came through the winter just fine. However, I have been periodically watering this tree, because I have several blueberry shrubs growing nearby, and I want to maintain ground moisture required by the blueberries.