How long have they been in the ground? If they were planted this spring, they probably dried out. Most new plantings need an inch of water a week. Watering them every day will kill them just as fast!! Bag worms could be the culprit, but you would probably see those on the plants. Like Ken said, attach photos.

T. Plicata 'Green Giants' grow taller in a manner where after each growth they have shot up a 4 inch or up to 3 feet tall main leader stem that is not very filled out. I do not suggest that stem should be cut off. Some people do it, but it's my opinion that the tree takes on a better growing form if that top slender main leader trunk is allowed to continue to develop. I have noticed that the tree along with its skinny top main leader will fill out much better if the tree is given some slow release food, during each spring and fall, high growth spurt. The non burning 3 or 6 month, slow release Osmokote fertilizer works well for my Green Giants. In addition, if yours are planted in clay soil, try to keep the soil only slightly moist. Otherwise the roots will struggle if the clay is allowed to remain too soggy. Such a conditon will drastically slow down the tree's growth and will even cause it to suffer more if once the soil gets dry and hard. On the other hand, if your soil where they are planted is quite sandy and drains rapidly, you will need to water your trees very often, and also often put down and mix into the soil lots of well processed, compost.

I have 9 Thuja GGs planted along the north side a Privacy fence, which is only 5 feet just north of a Brick, two story house. They receive mid day and full afternoon until sunset direct sun. In the winter mine stay green and do not show any bronze color change of the leaves My native soil is a dark, slightly acidic Clay. These trees benefit from the entire length of the fence area being slightly sloped upward and The soil along most of the fence has some builder's sand that had not been cleaned up by the workers who built the neighbor's house. This area is in the north east corner of my lot. My trees started out as one gallon pot sized trees, which were 12-15 inches tall and very nicely shaped and filled out when I planted them. These trees have been very happy, have grown to a height of 9 feet tall in Summer of 07. I watered them often especially in drought times, but did not begin feeding them Osmokote until the Spring of 07, which was early in the 3rd year since I planted them. When I was not feeding them the previous years, they sent up very narrow shoots of new growth each spring and fall. This new growth never seemed to fill out very nicely and by the time they reached 5 feet tall, they began to look pretty unbalanced. Once I started giving them the Osmokote, though, they began growing faster and all the very thin top half of the tree began to fill out more quickly. This made the trees appear much more balanced and more like one would expect the trees to be. Since my trees were watered, but not fed for the first two years they only grew about one additional foot the first year, and two feet the second year after I first planted them. When I began giving them the Osmokote, they not only grew more filled in tops; they also, grew an additional 5 feet in one year. I have a friend whose trees are planted in clay with out the benefit of added builder's sand, and they are planted on the South side of a privacy fence, which slopes from west to east at a fairly significant grade. At least half of her trees have needed to be replaced due to them sufficating along the lower part of slope, where the clay soil remainded wet for extended periods of time. They were never in standing water. The problem happened because runoff water kept the soil too moist for too long of times. The replacement trees she planted lived, and it appears they lived under the same conditions due to them being 5 gallon potted sized trees which were already 6 feet tall, when she planted them, and so we figured large of a tree needs more moisture than the original 12-15 inch tall ones, which died for her, needed.

How wide is the area? I would lean more towards some spruce or pine trees... maybe a mixture of the two. But if you want privacy faster... the trees your talking about are Thuja Green Giants... they grow around 2-3' per year. I purchased some of these last spring that were maybe 1.5' tall in 1 gal containers from Great Garden Plants... by fall they were around 3'.