I my friends did not write this either. I cannot comment on the Atlantica, as I did not sail on it. But someone here does have a valid question that needs to be answered. I advise you to seek medical attention.
I returned from sailing on the Atlantica this past Sunday, 14 March. I know of no one that suffered any type of digestive problems. We were with a large group and I talked to over 100 people on the boat and I heard of no problems. That does not imply that others do not have problems. We ate in every restaurant and buffet on the ship. I heard of problems on other ships but nothing on the Atlantica.