This singing group needs at least a themed backdrop and props, since they appear to be performing in front of a closed storefront; potted plants, boardwalk paraphenalia. The group needs some sort of a wardrobe coordinator, because they just look like 28 year olds going on a weeknight Target run for toothpaste and beer. Do they need full 1930's accurate costumes and wigs? No, but they need something far better looking and more cohesive than what they are wearing.
And what's with the very sloppy stagecraft?!? (This is not entirely the group's fault, it's mostly the fault of the management that allowed this to go forth in front of paying customers at a "Deluxe" property without funding an effective stage manager or appropriate support) I've seen groups performing at hippie streetfairs with better stagecraft and showmanship. They've got their 64 ounce Big Gulps left on speaker boxes, backpacks and more Big Gulps thrown against the wall, sound equipment just plopped there on the ground, etc. And what is with that weird rope thing as their stageline?