You could just copy paste the X value of each sprite. But I am guessing you would want to do it dynamically?
If so, it's best to use a placeholder that will cover the whole length of your health bar (it can be hidden at run time). Then you merely take the width of it and divide it by the number of health heart you want, then it will be the same distance
Also, the problem with copying the X is that all of the placeholder squares were made individually, so all their origins are different. So they would not be on the same position unless all of their origins are the same which I don't know how to do without deleting all of them.