I’m no expert - not even smart - but if it were me, I would:

Avoid all fruits, dairy, and high fiber foods. No Vitamin C tablets. .

Stick with rice, just plain white rice plus sips of Gatorade or Pedialyte to prevent dehydration, until you see improvement. Not too much liquid. Liquids are necessary for hydration but they can also trigger diarrhea and diarrhea is one cause of dehydration.

Then, once things are improving, try adding some chicken broth into the rice. Then wait. Next, try a small amount of jello to test. Then wait. If ok, then more jello. Then wait. If things are ok, add cheese a small amount at first. Then wait a bit.

If things are improving, try bread, potatoes, and other easy on the tummy, mild foods.

(No BRAT diet, the apples can cause loose stools.)

Hope this helps you.