Are these emarald green arborvitaes? if they are they need full sun as opposed to the nigra type that does better in the shade .Perhaps the fence has contributed to getting less sun.

No, your plan isn't correct. Adding potting mix to the planting holes won't help.

As for "acid levels," what level are you talking about?

Problems such as your trees are having are often related to water -- typically too little to the original rootball.

How have you watered them since they were planting? Critical info is how often, how long, to what area, and by what method.

For now, you need to determine what the condition of the rootball soil is -- wet, moist, or dry. Stick a finger in it to find out.

I'd have to agree with Jean - your plan is not going to help and could possibly make things worse.

Without seeing the specific conditions, I'd put my money on these plants receiving insufficient water during the growing season. During their fisrt couple of seasons in the ground, plants will need frequent deep watering to help them establish a good root system. How often is dependent on the climate and the soil conditions. Rocky soils often tend to be fast draining, requiring more frequent watering. Even slow draining clay soils may need regular summer irrigation. Allowing the original rootball to dry out might have compounded the situation - once that happens, it is difficult to rehydrate and the problem is exacerbated.

If soils are heavy or difficult to plant in, a wide shallow planting hole is recommended. Use only indigenous soils to backfill - no amended stuff or potting soils. Make sure the rootball is thoroughly moistened before planting - soaking in a bucket of water for a period of time can help. The plant can be left high (if poor drainage, this is a good practice) with the top of the rootball above grade. Mulch to cover to the crown, keeping it free of the trunk. Plants will need a minimum of 5 gallons of water per inch trunk diameter per week during the first growing season. A slow, gradual application that penetrates well down into the root zone, as with use of a soaker hose, is best.

FWIW, one of the other common names for arborvitae or Thuja occidentalis is swamp cedar - it is difficult to provide these trees with TOO much water unless drainage is very poor.

Wow my wife and I are (pleasantly) shocked at the possibility of not enough water. Here is other information I meant to include:
These are emarald arbs.
Most of the arbs on the east side have the top 12 inches drooping over at this time (Oct). I thought this was from too much water. The water drains from North to South and 'moreso' West to East. A PICTURE IS WORTH A THOUSAND WORDS, so I posted the pictures to get some help to save the arbs www.kodakgallery.com/dawksphotos. These are from 8/24. Take a look at the last 2 'distance' pictures to get better idea of the overall landscape. You can see how green the grass is on the west side from us watering them, while the rest of the grass is mostly brown.
You can also see the shade of the privacy fence on the east side blocking the morning shade it used get. At noon they get sun.
From the time they were planted through the summer, they were watered at least 3 times a week by us or mother nature. I noticed there was a question "by what method" did we water them. In August it was very dry but we really watered them a lot by using the hose (not soaker hose) for about 2 minutes each arb.
The nursery also mentioned being careful of something called "wicking" where they advised making sure the burlap was completey covered by soil (mulch etc.) They described this as drying the rootball due to the water flowing down the outside of the burlap away from the root, so I made sure that the ones with burlap had the burlap covered.
I'm holding off on changing the soil to help it drain on the east side for any other responses and will continue to water it.
There are close-up pictures of the arbs labeld L or R for West and East respectively, and 1 through 15 or 16 going south to north.
I am going to add pictures to that site for what they look like today.
Thank you very much for your continued responses.

You wrote: "my wife and I are (pleasantly) shocked at the possibility of not enough water."

You won't know for certain until you poke around the rootballs.

As for the photos, 11 is dead, probably also 25.

Dig it/them up and look at the roots. Also break apart the rootball to see if the interior is wet, moist or dry -- that will help answer your questions.

Here is a link that might be useful: Your pictures from August

1 looks dead, 2 more not so good but the one with the small amounts of brown branches will be fine I think. It looks like the handling of thenm might have caused that, just keep watering and provie as much sun as possible

I placed the pictures for Oct 4th on the same site www.kodakgallery.com/dawksphotos. Thank you for all the advice. The soil around the rootball has been moist to wet. The arbs get brown from the bottom and inside, then browns straight up the inside center, then the top curls and the browning makes it to the outside.
We really did water these a lot, but if the 2 biggest responses that the arbs need more water are from gardeners in the PNW, then I'll keep watering and see what happens. Again thanks so much for sharing information. DK53