[Boatanchors] Do Inductor values ever increase with age??

[J. Forster]

I can notmthink of any reason why inductors would increase in value, except for ones that have an air gap. Small changes in that gap could cause a dramatic shift in inductance.

That said, IMO the cause of the problem is more likely your measurement technique. You are modeling the inductors as a pure inductance.  That's not true to life. They have a DC resistance, not negligable in such high value chokes ( as well as stray capacitance and other factors such as core loses) The reactance of the choke is the vector sum of the inductive reactance plus the
resistance.

Also, are you measuring the LPF cutoff frequency with the filter sourced and loaded as designed?

John