I did do a check but couldn't see anything still attached to the seed or any excess material.
At least I know it wasn't through any error in moisture level or handling that this has happened. The seedlings that are growing seem to be a fairly varied mix so I would prefer to keep them alive, more so for the curiosity of knowing what they actually are.
Where do you get sulphur from?
I will consider using it next time, will have to do some research to see if it will have any affect on the seedlings that have already sprouted.
I'm hesitant to dry them out yet, the seed being a mix has germinated at different rates and some have been sprouted for a few weeks others only a few days.
Perhaps that will have to be considered though if this fungus thing is going to rear it's ugly head again.
I had to remove the cover for one lot of seeds I'd planted (alenopsis rubrolineata) as the seedlings refused to stand up and the stems were breaking, out of the 5 that germinated 2 are still standing but since removing the lid they have halted and have not showed any sign of growth in several weeks now.
They do still appear healthy but just refuse to grow. I'm assuming that would be the same outcome if I were to remove the cover for the cacti mix container.
Guess this is all a learning experience, being first time growing cacti from seed.
Thank you for the replies.