I'm having this issue as well. Both my mermaids have the Child of the Ocean trait and both have been getting the upset stomach "from eating fish" after eating the Kalua Pork. Now it just happened with the chicken you can make with the Sulani Volcanic BBQ Searer. The animations when they're eating it are similar to when they eat spoiled food, or when vegetarian sims eat meat. I just had one eat the Pork Adobo though and, so far, that still seems fine. It also hasn't happened with the vegetable feast.
Here's a screenshot of my Child of the Ocean Sim getting the "Stomach Squall" moodlet from supposedly eating fish when she was actually eating the roast chicken you can make with the volcanic BBQ Searer.
