In a group check like this, the "middle value " is the one that counts. Rodrigo is competent at stealth, but he rolled poorly, so here we are.So.. We have 17, 14, 11, 4, 4. Stealth. Meh.
I usually like to work under the assumption that the PCs are competent, so it's gotta be mitigating circumstances that cause you to fail.
There's your surprise round back, if you want it...