UPS shipping- item weighs less than 1 pound

I have seen posts for heavy items but can’t seem to find a post for items that are light. I carry candles and setting the weight at zero returns a charge that is approximately the same as the charge I pay the company. The problem is if I have a customer that orders various candles, etc that have a zero weight, it isn’t going to increase the shipping although my shipping (what I pay) would change. This is further complicated by the fact that I have several different distributors where I have to set the weight at zero to get the correct shipping for one item but it isn’t going to work if they order several different things.

I need a shipping guru to weigh in (pun intended) and help me resolve this.

Thanks!