Metal dome tweeters can be pretty unforgiving, but swapping out a tweeter is a significant undertaking to get it right. The whole crossover is built around implementing those specific drivers together....more so with Snell than most, because they actually tweak the values for each set of drivers.
Do those tweeters happen to be ferrofluid cooled? If so, it might be time to clean it out of magnet gap and replace with fresh FF.
Another you thing you might consider is to upgrade old caps and resistors, especially if there are any electrolytics in the tweeter path. You don't need to go crazy with expensive boutique caps, but a decent basic polypropylene film cap like a Solen, Sonicap, Audyn, etc, could help clean things up. Be forewarned that IME, good caps take some time burn in, and may sound quite bright and brittle when new, but have patience, they'll come around.
Most of those old cast resistors have an inductive byproduct that doesn't help either. You can replace same values with wirewound non-inductive types.
The protective fuse isn't helping the signal path sound any clearer either. If you don't crank on them, you should be able to bypass the fuse completely and get it out of the circuit. All minor possible improvements that may help give those metal domes a slightly cleaner signal. Food for thought...