I have a row of ten Leyland Cypress trees planted from 3 gal pots at 2 feet height on the property line 4 years ago, in full sun all day. They are now over 8 feet high and (until recently) have done very well. One of the trees has turned brown from the ground up....and is now 1/2 brown, easily apparent on either side of the tree, green on the top 1/3 only (see Picture 1). Most all the other trees look good from my side of the property line, so far. There is evidence of two other trees similarly beginning to turn brown from the bottom...but ONLY on the other side of the property line. The trees are on a gentle slope and the area drains well after rain. Occasinal hand watering when dry in the summers. 10-10-10 applied early fall 2018. Close to an area where lime on fescue grass was applied also in the fall. I have included pictures. I am worried as I see a few locations on Rte 2 near Owings where 1/2 of thirty beautiful Leyland (or similar species) are turning brown, some much worse than mine and completely brown. I am in zip code 20639.  Pictures included. I can send more pix if needed. I noticed this in mid-Nov...it seems to be progressing slowly. Is the one 1/2 brown tree going to infect the others? Is this a fungus or insect problem? Should it be pruned where the brown is? Completely Removed? Spray something on it? Wait till Spring? Thank you very much for your consideration.