Question
I don't believe drainage is the problem. The schrubs are located in 6 separate regions in the yard, some in the back, some in the front. The schrubs that are by themselves showed the problem initially, then the grouped shrubs started to exhibit the problems. It's now affected about 7  of the 20 & seems to be continuing. All the schrubs had new blossoming growths & were growing like weeds. I hosed down some of the "bad" schrubs. many small brown moths flew out of each schrub. The schrubs have been in place & healthy for over 15 years, do you have any ideas on what may be killing them ? 2 are now totally brown.

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Followup To
Question -
I have 15-25 evergreen shrubs, all about 3-4 feet wide, 3-4 feet high. Many of the shrubs have brown needles/branches & whatever it is eventually is causing the entire bush to turn brown & it looks like they're dying. Many of the plants are still healthy in appearance, but many of the plants are in various stages of degradation. The brown needles start at the top of the bushes & progress until they include all the needles.
Answer -
Hi Gene
check the soil for drainage browning needles usually indicate a soil problem.   Good Luck  Larry  :-)

Answer
Browning leaves usually indicate a soil problem, other than that if they are that old then the problem is enviromental, weather conditions such as excessive rain high humidity strong winds or very dry conditions will give the same results on the shrubs.  all of these factors
affect growth and development. things like over watering and over fertilizing will also brown the leaves/needles but that is controlable sice the cause is manmade. i still beleve the problem lies in the roots but you could consult a landscaper to look at the problem first hand and do a site analysis.   he will probably suggest replacement.  Larry