I’ll chime in since no one else has yet. I’m no expert on salt but I have done quite a few long ultra-type endeavors in some extreme conditions. And I live and train in the deep south where it’s hot/humid more often than not.
I myself do not supplement with salt tabs. I rely on what is in the nutrition I take (gels and mixes) and that suits me just fine. Many of my training partners swear by salt tablets but the few times I did take them I experienced issues (usually mild – finger/hand swelling) and do not feel they added any benefit.
I would suggest that your problems on that particular race had another cause, perhaps going out a little too hard/fast for your fitness at the time.