I would put money on this being a torque or scope issue. Even though things are loctited, take a torque wrench to every single screw. Bases, rings, the lot. Do the same for action screws. I've seen loose action screws cause weird weird events.
Once physically torqued (not just assumed or looked at) take the suspect ammo and another known ammo and shoot groups side by side. This will give you most of the needed data points.
If both groups are good, then you 1) had a trash day, 2) you need to look at the powder and temperature difference, or 3) start testing shooting positions to see if your groups go to heck with forward stock pressure (like a bipod) or something similar.
If both groups are enormous, then your scope died.
If one ammo groups well and the other sucks, then you can look at your ammo details and see what happened.
Isolating variables is the only way to verify this. Keep your shooting form good, let the gun cool between shots, take your time and ensure the shooting platform is the same for everything.