WNBA Star Kelsey Plum Claims Jamba Juice Smoothie Causing Bad Diarrhea

WNBA star Kelsey Plum is having a pretty crappy Monday ... and she says it's all 'cause she drank a tainted Jamba Juice smoothie!

The Las Vegas Aces point guard took to Instagram to explain her plight ... writing on her IG Stories that she believes she's battling some bad diarrhea this week due to some extra berries she threw into her JJ drink over the weekend.

"Peeps," she wrote in a warning to her followers, "stay away .... I ordered double strawberries this weekend and my butt paying the price."

In her social media message, she shared a screen grab from an iwaspoisoned.com article that reported Jamba Juice has recently issued a caution to its customers about its strawberries -- saying they recently might have been contaminated with Listeria.

Despite the situation, Plum's clearly taking things in stride ... as she included some funny emojis on her post.

The WNBA season is currently over -- so Kelsey's got all the time she needs to recover.