Because you were above 5000MSL what was your pressure setting on altimeter,
standard? You mentioned cold front, low pressure? Are you sure about your
altitude in standard setting? If fighters were at 6000 on standard setting
and also you but because you were using MSL setting just didn't know that?
These helps to understand (I hope) why you two were so close to each other
and it is good to go through why this could happen.
This sounds like I am blaming you, but I don't, as an outsider I am able to
see also probably mistakes you have done.

Ari