I honestly wouldn't be surprised if they HAVE to wear the same dresses, so that when the show is edit to be aired, they wear the same dresses all the time too.
But, I know nothing about this stuff so I might be talking bullcrap
They're going to make it seem liked the Austin auditions were just 1 long day
Or they're doing this because yesterday was the 1st day & they were just warming up so they will appear to be more comfortable this round while it still looking like the first audition destination.