Treated my interconnects with Deoxit D5 today

I had the same problem with D5, i.e. washed out sound. However I also use what used to be called Deoxit Gold ( the company seems to be changing the names) and that was quite the opposite, i.e a big improvement in sound quality. As I understand it the D5 is a straight cleaning fluid, the Gold is a cleaner plus a contact enhancer presumably it adds in some kind of fluid which is conductive. Possibly what we both found was that clean contacts don’t actually sound that good or the D5 leaves some kind of film. Irrespective, I just added an application of Gold and was very happy.    

I bought Tweek years ago, it evaporated in like a year or two, even though it was sealed tightly

You were fortunate.

Stabilant 22 appears to the equivalent to Tweek.  It is about $60 for a vial of it which should last for years and years.  Check out their website as users of it speak in glowing praise of it, including lots of technicians.  I am just happy that my system returned to its former splendor.  There is an old adage that says, "if it ain't broke, don't fool with it."  

I’ll go out on a limb and say they’re not equivalent.