I meant to ask you this last week, but forgot. Have you considered removing the dirt that’s there and starting over, or has anyone who’s quoted you work suggested that?
I work in the field, and a guy I work with had a customer when he owned his own business that had a similar issue to what you seem to have. He said he removed all the loam and replaced it with new material. It was costly, but worked, and this was after several attempts to use what was there.
Like was mentioned to me in that discussion, it’s possible the dirt could have been contaminated in some way, or something along those lines. Or it’s simply just not a good batch of dirt and doesn’t support healthy growth.