Move the bulb back to about 4 - 6 inches and slow down on watering slightly.
The picture is fuzzy but it looks like it's already burnt and you might be better off to scrap it and germinate another.
Never had much luck with germinating in rockwool, I have given up on it, and switched to perlite and vermiculite. I find the seeds have a hard time getting out of the stuff and are stunted once they do, if they do at all.
The picture is fuzzy but it looks like it's already burnt and you might be better off to scrap it and germinate another.