We have a large evergreen in our backyard. It gets good sun light, and I think enough water. In the past month we have started to see a ton of needles shedding. The branches appear to be thinning out, we can now see to the center of the tree. some of the needles remaining are green, but a lot are gone. What do you think? Is there a nutrient it's lacking? The tree is about 40 feet tall. Please let me know. Thanks for your help! Gina Roache.