If it's really a "wilt", here are 3 possibilities

1) Armillaria root rot. Look in the pot for black "shoelaces" among
the roots, or notice golden mushrooms growing in the pot.

2) Verticillium wilt. Take a tree you know is a goner, and whittle off
the bark until you hit the first few rings of wood: do you see brown
streaks?

3) Pine wilt, caused by a nematode. You'd need to take a sick tree to
the nearest Cooperative Extension office to diagnose this.

However, I find it hard to believe that all your tree could catch a
root disease, unless you submerge your pots to water them and share the
"bathwater" among the trees. Root diseases aren't very contagious as a
rule. Take a good close look at the yellowed branches for signs of
larch casebeares or larch beetles (do a google image search to find
pictures of symptoms).