Using rockwool cubes which had clones in them which did not start..

So, I would to like germinate seeds in rockwool cubes which I used for clones (picked 5 weeks in flowering )..which didn't start +they where dipped in rooting powder...
So re-use these same cubes...or do you thing there is some contamination from the stems and rooting powder ?
they sat rooting for 9 days and didn't root so I decided to start from seeds rather...(I am out of cubes other vise, and why not recycle these ?)

i would buy new cubes or jiffys

Didn't make it to the store...soaked the cubes in ph water included with Hydroguard which should create a pathogen free environment with beneficial bacterias...