Asked January 13, 2021, 9:30 AM EST
Montgomery County Maryland
We share your disappointment with the loss of your beautiful tree.
According to this page from Oregon State University, we think that your Cedrus trees may be the same: https://landscapeplants.oregonstate.edu/plants/cedrus-brevifolia
It's impossible to say for sure what took out your tree but it is likely a combination of factors, first environmental problems which stressed it, and later insect issues that moved in related to the stress.
Unfortunately these trees are native to mountainous regions of Cyprus with climates that are drier than our area here in the mid-Atlantic U.S. They are labeled with a cold-hardiness to zone 6.
Given climate change, it's getting more difficult to predict how plants will respond. Within the last couple of years we have had significant periods of historically high rainfall, interspersed with periods of drought.
Once stressed, trees are more likely to attract insect pests like borers, which could be the reason for the sap flows you are seeing. Evergreen trees are notorious for being slow to show damage or symptoms until they are essentially dead- think of Christmas trees that are literally disconnected from their roots for weeks or even months before their needles brown. That's why it sometimes seems to have "almost died overnight".
You might wish to pull that tree out and examine the roots and nearby soil to see if it is wet there and there was root rot (healthy roots are white).
We wouldn't recommend replacing with the same type of tree.
For your other one, you could consider having a Certified Arborist come and assess the health of the tree and what might be done to help it along. You can search for an arborist that is credentialed by the International Society of Arboriculture (ISA) at their website here: www.treesaregood.org You should consider having more than one give recommendations and compare.
You are wise and on the right track. Good luck.