You are probaly watering them way to much. I live in a much dryier climate than you and the only thing that I think about watering every day are plants in pots in 100 degree weather. I dont even water my blueberrys every day, and they cant dry out at all. So leave your water off for a few days/weeks. If you are not sure dig a hole and see how dry your soil is. I understand that the most common reason trees fail is they are over watered.

I have to backtrack a little and explain that when I planted the first set of trees, I was a COMPLETE newbie. I did not even have the soaker hose down at that point. I was watering them by hand about once a week thinking that would be enough. The soaker hose is that flat fabric kind and I've got two of them connected to a "Y" at the edge of my house...one length that goes down the side of the house is 25 feet, the other length goes toward the yard 50 feet. Together they make a 75 foot run and I read that a length under 100 feet should not be an issue where equal pressure is concerned...am I wrong? There is no "incline" along the length where the water ever has to go uphill, that is an optical illusion. From where the water enters the hose it only goes downhill slightly. I've been using this soaker hose all summer and it seems to do the job well, although I had to use it every day since I did not have time to put mulch down until this fall. I am thinking the reason the first batch died was from obvious lack of water before going into winter and then drying out by spring. Also not having mulch might have been a factor since we got down to -5 last winter. I have a hunch that the drying winds knocked out most of them, since my few survivors were the ones next to the house where they are somewhat protected. Which leads me to another question... What do you think of Wilt-Pruf? Could I prevent some dessication by using it? I was going to go with burlap but that is an awful lot that I would need to wrap...do these even need protection from wind if they get enough water before winter? I think in the spring I will move the one arb with the dead branch to the end of the line and replace it so I can keep the height I have going in that area (I need it there! I don't think want a window in my hedge..haha).

Thank you all for the replies and thoughts. When I removed the burlap, the clayey root ball seemed very moist, so I believe it was adequately moistened. I have since placed a soaker hose in my garden bed (under 2-3" of mulch) with a full loop around the base of the tree, so we'll see what happens with soaking for a longer period of time rather than 5-10 minutes of direct hose spray. I also want to note that I planted a new rhododendron immediately adjacent to the emerald green about 2 weeks ago, and I just noticed today that the rhody appears to have a disease, which looks an awful lot to me like phytophthora ramorum. I think I have heard that arborvitaes are also susceptible to this disease. Do you think there might be a connection between the rhody and the arborvitae? I am probably going to pull that rhody out and bring it back to the nursery where I got it, as it was only a few weeks ago. I posted photos of the browning arborvitae foliage, and of the rhododendron.

Thuja are a titch more demanding than most trees in the fertilization department, being fast-growing, but don't generally require a specific fertilization. But it's certainly an option if the OP would want to. In my case, I pushed mine from three feet to twenty in eight years to cover a particularly obnoxious neighbor, but that was an exception to the general rules... Although I'd recommend a low-powered organic one and in smaller amounts due to the lower amount of space available and on the lower end of the pH scale due to the preferences of the family to begin with. As I think on it, pH can be an issue, but most Thuja adjust well and aren't that particular about it. Still, as noted, excessive salt additions not only add sodium but boost the pH toward the alkaline. Which can cause some spotty browning. It's not of any concern, and the standard fix (yellow sulfur) is generally ineffective. But it's another possibility. And the only way to be sure is, again, a formal soil test. The home ones aren't accurate enough to be sure. Off the cuff, a small amount of Holly-Tone or Milorganite (fairly neutral, but does contain plenty of iron sulfate, which is acidic and the sulfates happily locate calcium, magnesium, and sodium and bind to them and remove them as highly soluble salts) wouldn't be taken amiss. But, of course, it's absolutely optional. If all this were me? I'd be out there with a fine clippers removing the brown tips. Because I'm seriously that picky. Been there, done that on my Green Giants.