I've fed my 2yr old labrador on James Wellbeloved kibble since he was a pup, he weighs 27kg and has a lovely glossy coat. His poo has always been softish but formed and easy to pick up iykwim. Over the past couple of weeks his poo has been very soft, he's not had anything new to eat. Would it be worth trying to change to a different kibble?
As there's only been a problem for 2 weeks better to stay on same food, changing can upset their stomach. If poo is just a bit softer but otherwise normal could be due to eating a bit more than usual. Or snacking on walks. My lab manages to grab mouthfuls of stuff in passing even when on lead, amazing how much food people drop, half eaten bananas, bread rolls etc.