>>3753757>Three pictures turned out like this in the middle of the roll right before 4-5 frames that were completely blank.
Then it sounds like the shutter didn't fire properly. Could it be dying batteries? Did the rest of the roll (after those blank frames) look normal, with the same batteries? Even wrong iso doesn't give totally blank shots, though a couple stops of underexposure could be due to accidentally turning the iso dial or EV compensation.
Also no it doesn't seem like a lab issue.
Is this the first roll you're shooting? Or you shot multiple rolls and this just happened for the first time?
Usually a blank shot means the shutter didn't fire. That could be either to dead battery, or bad connection somewhere, or more rarely some dirt in the electromagnets (for electronically controlled shutters), or even more rarely a malfunction in the circuit board of the camera.
Those things can be intermittent, so it's not unusual to have an issue for a couple frames every X amount of frames, with the rest turning out fine.