I pulled out the current noisy/soft lifters and manually filled them with oil by hand so they were stiff. Put them back in, turned it over a few times and then ran it. They stayed stiff and were all quiet. Left it over night. Checked it in the morning. Still stiff. Came back an hour later, checked again, some were soft and the issue was back.
It seems like the lifters have the ability to hold pressure. The car just isn't pumping them back up fully if they leak down. I have nothing indicating that the pump is bad but I don't know what else it could be at this point.
I feel like I can rule out the lifters.
I have replaced them, checked them and tested them.
I don't think it's mechanical wear of any kind for the following reasons:
The lifter preload checks out, it's not a consistant issue, it comes and goes and it seems unlikely that they would all go bad all of a sudden.
Nothing was changed on the car before the issue started to occur which means its somthing that has developed on it's own.
I think the pump is all that I'm left with.