splayed legs are usualy caused by lack of support in the nest, for example with canaries its usualy caused by the nest cup being too wide, and in budgies its usualy cuased by a lack of nest material and lack of siblings to lean againt so the legs slide out to the sides and the chick grows up with splayed legs.
it can be cured at a young age by putting a closed ring on both feet and tying them together at a normal bredth for a couple of weeks.