Urban Outfitters has likewise lost some traction with millennials, having failed to deliver on its reputation for unique products, Jaffe said. Now under new creative direction, he's hopeful that Urban will regain its identity in the second half. According to Chen, it's carrying differentiated fabrics and looks creative, but the assortment "remains a work in progress."
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As for the other teen retailers, Aéropostale is trying to become more relevant with its target customer, including a partnership with YouTube star Bethany Mota. To highlight this shift, the retailer's website has been running with the tagline, "You've changed, so we've changed."
American Eagle's strong focus as a denim destination has Jaffe nervous, he said. Denim purveyors VF Corp and J Brand expressed weakness in the segment in their most recent earnings reports, as consumers' interest in activewear and dresses has pulled spending from the category.
A few footwear trends are also expected to steal some wallet share. Rechner said she expects Deckers' new I Heart Ugg line, which targets girls ages 9 to 13, to be popular, while basketball footwear will likely continue to be a top seller for boys.
And with the expected launches of the latest iPhone and Samsung Galaxy, technology and tech accessories will also capture consumers' dollars, Jaffe said.
"That's a scary thing for apparel retailers," he said.
Another issue that should concern retailers: the weak spring season offered no visibility into which trends will resonate this fall, Jaffe said. When spring sales are strong, it's easy for retailers to see which styles the early adopters are snatching up. But because spring selling never really took off, it leaves a lot of guesswork.
What's worse, if no must-have item emerges, it'll be challenging to get shoppers to pay full price, Chen said.
"Kids won't do without, they will buy new clothes," Jaffe said. "It's going to be a challenge who gets that market share."
—By CNBC's Krystina Gustafson