Nutrition experts: Orange juice/tomatoes and diarrehea!

I always have some diarrhea with herceptin but it's been more than two weeks--next one is Tuesday, and this weekend it's been more severe.

I noticed it yesterday when I got up in middle of night (couldn't sleep) and had a tomato sandwich on toast and large glass of orange juice. Nausea and diarrhea followed, and then all day. Just had another glass of orange juice, cut by seltzer water and again diarrhea.

Can the acid in the orange juice be doing this. I'm a first grader when it comes to good nutrition. Thanks.