Breathing Difficulty with Palpitations.

"I had been taking Shelcal XT for about 2.5 years. In my recent blood test, my Vitamin B12 level was high at around 2000. Shelcal XT contains: Elemental Calcium – 500 mg Vitamin D3 – 2000 IU Methylcobalamin (Vitamin B12) – 1500 mcg L-Methylfolate Calcium – 1 mg Pyridoxal-5-Phosphate – 20 mg Since it contains Methylcobalamin 1500 mcg, I think my B12 may have become high because I took it for a long time. So my doctor advised me to switch to plain Shelcal 500 and Ultra D3 2000 IU. I stopped Shelcal XT and for the past 3 days I have been taking only Shelcal 500 and Ultra D3 2000 IU. I was fine all this time, but for the last 3 days I have been feeling mild breathing difficulty and mild palpitations. Is it possible that these symptoms are due to changing the tablets 3 days ago?"