Bridesmaid hair and makeup

Hi all, so I was planning on paying for one of the two services for hair and makeup for my bridesmaids as a gift. I know everything can go either way to if I pay for both or neither etc. so I was originally going to pay for their makeup because it’s a flat rate. But after thinking, everyone is going to have very simple natural makeup so some of the girls could totally do it themselves. I want them to all have braided updos so i want to switch to paying for hair instead of makeup because it’s more of a must have to have the hair done than th e makeup because of the style. Our stylist charges more for thicker and longer hair so I would be paying extra for two of the girls which I’m fine with, but is that rude to the other two girls to be paying more for them. I’m doing this as one of their gifts so I don’t want it to turn into well you paid more for her than me. Would it be rude to have the extra long hair charge be paid for my the maids with long hair? I don’t want to be rude and want to be fair to all of them. What are your opinions? Thanks!