For the health of your flock, I would cut the corn right back to less than 10% of their daily intake or cut it out altogether. The pellets are a complete feed that give them everything they need to be healthy and produce eggs with strong shells. Feeding them grains dilutes those nutrients which means they are not getting everything they need to produce eggs with quality shells and puts them at risk of obesity but can also lead to reproductive issues as well as fatty liver haemorrhagic syndrome. These ailments are slow to develop so you may not be aware of the problem until it is too late or difficult to reverse the damage..... just like us eating too many carbs... but because chickens are operating at a very high level of production, like a top level athlete, their diet plays a much more important role.
Does it feel like her spine. Some of mine with Marek's develop a contortion of their neck/spine that causes it to kink and push out in front like that. A close up of the growth on her leg might help. How old is she? Losing body stores (being thin with muscle wastage) can also be a sign of tumours and/or Marek's.
Alternatively she could have an impacted and pendulous crop.... you didn't mention if this is separate of her crop. That will also cause her to be thin as nutrients are not able to pass through her digestive tract. Oil and massage would be the first course of action with an impaction and access to only very mushy food with no grains or fibres, so she would need to be isolated in a dog crate or similar with no bedding other than newspaper or puppy pads and only have a thin watery mixture of pellets and feed with some Nettex Nutri Drops added and a teaspn of oil.... solid coconut oil works well and crop massage 3-4 times a day for 10 mins each time.
