Goslings losing feathers

[CanadianChix]

I was wondering if my goslings and 1 duckling being too close to the heat lamp could cause them to lose feathers just in their back. The two tallest have the most feather loss but only on their back one is a Toulouse Dewlap and there are no other symptoms they are healthy eating running around but they are tall for their brooder I thought I saw a thread on this on here anything helps

 

[Miss Lydia]

How old are they and what is the temp in their brooder can you post a picture of your set up?