I'm not sure how much harm it's going to cause by leaving it there but, if it's not too much trouble, try removing some of those rock pieces into a bucket with some of the tank water and run a powerhead for a few days.
I once asked a seller to cut the rock into a smaller rock before shipping out my shroom. He sized down the rock with his bandsaw, he did a good job. But when I got the overnight, the shroom was completely melted while another shroom in a separate bag did just fine. He thinks that the freshly cut rock released some sort of toxins in the water when packed. He said he should have kept it for a few days before shipping. I think there is some truth behind what he said. It was a semi-large Magic Carpet shroom he had for about 3 years. Those things are hardy, they don't just melt completely overnight. Just wanted to share this story in case in helps.
