Imhififan,
For fun and a further learning experience you should try replacing what certainly appears to be steel fasteners holding your crossovers in place. I would do only 1 at first as my guess would be an imbalance left to right. Probably need to settle in for 12 or more hours. If you do hear an imbalance or change in response then do the other speaker to match.
My preferred fastener is brass a non ferrous material.Steel will bend the intended field of flux.
I did this 20 uears ago replaciing steel fasteners with brass in and around the crossover of my Dunlavy SC4.. Then replace the cast resistors for Mills or Path for simple and quality upgrade. TomD.