This is good advice on the need for four new tires…However I do not recommend having a new tire shaved…first off you’re voiding the warranty and secondly you’re depending on a tire shop guy to determine the shaved tire’s circumference as compared to the other three tires (which probably are not the same anyway).
Perhaps the tire dealer will give you a deal for the three replaced tires or you can take them home and sell them on ebay.