Hey Growmie,
The humidity should still be fine at 60%. This is going to be the result of damping off.When a seedling has already toppled-over from damping-off, there is nothing you can do to recover it. The best you can do is quickly remove the affected seedling together with its cup to prevent the spread of disease to other seedlings. Hopefully this was helpful and I wish you nothing but success on your future endeavors.