Thank you for your reply's
Day 7. Today I had some problems with the eggs.. On the right you can see an egg which has enlarged, I think it is due to osmotic pressure. On the left is a dead egg swirling but you can also see another dead larvae, it's the one with the white spot on the egg. So lost 3 larvae at this stage. One of the larvae hatched premature, my fault I guess because I rinsed the eggs out of the tumbler so I could clean it... When I put them back gently it hatched..
I did a small water change, about 25%, using warm water to refresh to keep the temperature the same. I then put a blanket on top of the tank to make it dark where the eggs are in the tumbler.
It seemed to have worked and the larvae were ok the next morning. I did another small water change today, same routine. Even the premature hatchling was doing fine and had even grown during the night! So a bit more hopeful
Day 7
https://youtu.be/pO0yDe8Rs9I
Day 8, top view
https://youtu.be/-PiMroe93xk
Day 8, side view
https://youtu.be/qsgLCyaZqmU