Stream lagging only on OW

(First, sorry if I do some english mistakes, I’m french Canadian)
Hi! So recently, my stream started to lag but ONLY while playing to Overwatch. I tried everything, updating my gpu, looking in my settings of Streamlabs OBS and Overwatch. But the issue is still there, people who are looking at my stream sees me lagging, even if In my point of view, I’m not lagging at all. I could use some help!

My GPU: AMD Radeon R9 360
My CPU: i7-6700