My parents have a gigantic arborvitae on their property that was already full grown 21 years ago when they bought the home. It did not appear to ever have been pruned, but just allowed to grow naturally. It has to be at over 30ft. tall & easily 15+ ft. wide at the base. Over the last few years it has slowly been thinning and browning evenly throughout. We climbed and played under it as children constantly, and a bit too emotionally attached to cut it down. Is there a way to restore life and fullness to it? There doesn't appear to be any bug problem, and the brownness and thinning is even all over, not just at the bottom, so we are stumped. Any help would be appreciated. Thank you!

Needle evergreens have been stressed since the drought of 2012. General plant health management would include watering during periods of dry weather, not just prolonged droughts and annual feeding. It took several seasons for the tree to look like this and will take several more seasons to recover. Be sure you water well into the fall, the last time just before you have to remove the hose from the spigot for the winter.