I think the question should be seen as a problem you can solve together, more then an accusation. So maybe phrase it more like ”I’ve observed a change in outpu

I think the question should be seen as a problem you can solve together, more then an accusation. So maybe phrase it more like ”I’ve observed a change in output from the team. Tickets seem to be taking lounger time. It does not seem to be due to x,y or z. What do you think about it?” People always rather be part of the solution, not the problem, so better to invite them to solving the problem with you