All sources of minerals utilize B vitamins and will deplete them in rapid succession. If you are taking mineral supplements, you will need more B vitamins

First take good food based multi vitamin 3 times a day along with either B50 or B100 food base of course, 3 times a day for a week, tachycardia or heart palpitation will stop within minutes. B vitamins will be depleted in around 14 days so you will need to take them regularly. For some reason it does not stop your heart problem, then your tachycardia is not caused by B Com deficiency but systematic candida overgrowth.
Best and most effective way to get candida overgrowth in control is to use a product made by solary called yeast cleanse, it has tea tree oil in them and is very effective in controlling candida. Best to take it with a product called Candex, which is a digestive enzyme for candida biofilm formation