My IBS symptoms disappeared with Vitamin D supplementation. Coincidence?

I used to have IBS-D that would appear frequently due to my regularly stressful coursework. My symptoms usually appeared early in the school day, before an upcoming test or due date for an assignment. If I didn't study/didn't finish the assignment, I was pretty much guaranteed to show symptoms. After hearing about the connection between Vitamin D deficiency and IBS, I decided to supplement Vitamin D (5000 IU daily, along with Vitamin K2), knowing that I probably don't get enough due to being inside most of the time. Afterwards, my symptoms improved immediately. It's been a full month now without IBS, which is rare for me. Was it a mere coincidence? I don't think my workload/anxiety levels have lightened up correspondingly.