We were on this cruise also and this is first I'm hearing of this. How disappointing that must have been. IIRC, Cartegena was the day before the transit, possibly too soon to show symptoms. Cozumel was 2 days before Cartegena and I was too afraid to take any excursions there just in case we'd get exposed and then have to miss watching the canal transit. We didn't even go to a beach.
We also sailed last August and November and never got covid until May when dh was exposed to a coworker. We are still in our 90 day recovery bubble of bliss. It's actually a great feeling to not live in fear of catching covid from someone nor do I fear giving it to someone.
It's a lot like the feeling of not needing to worry about using birth control while you're already pregnant.