I didn't have a problem with rockwool, but I only used 1x1", after I germ'd, and in conjunction with DWC...never in blocks or slabs. I can see where there would be alot more problems with it in those applications
now, through research and hanging around these forums...I don't use it except, as a starter after I germinate. It's just that it worked for me, so far...just my $.02 worth.
...later