Randomizer to blow up aircraft help

[Gunfreak]

So basically I have 16 German aircraft, on mission start I want to randomly select 2 of those, that can blow up if they get less than 70% health.
So I'm making 8 triggers each for 2 and 2 of the 16 aircraft.

However I'm unsure how to do it, so not both aircraft explode if one of them get 70% health...

To me the way I've set it up here, it looks like if either of those aircraft hit 70% both of them will blow up?