Searched for this and found nothing, hope it’s not a repost.
Using Detonating Arrow with Arcing Blast and/or (more likely) Multishot with Giant Slayer and Readied Arrows lets you stun the turrets so the bolts start to fire out of sync for the rest of the battle. They are untargetable so I think it has to be something automatic. My smoke bomb also has the slow effect but I don’t know if that would slow their activation/targeting speed.