Get something related to their individual interests and hobbies like you are shopping for their birthday. What do each of them like in their everyday lives? Anything that you intend to be worn or used on the wedding day is a prop for you, not a gift for them.
I would make the last gift something personal to each lady. That's what I did for my bridesmaids. I got them each a makeup bag with a lipgloss, hand cream, and hand sanitizer inside (clearance at David's Bridal), a custom print of all of us from Etsy, and then each of them got something more personal. I got my two sisters a book (we're all readers and are constantly giving each other books we've read), my one friend an Etsy gift card, and the fourth one a T-shirt from Amazon that read "Easily distracted by dogs and books":