Panda Cory Curved Spine

[silvercory]

I have 5 small Panda Cory’s about 15 mm long and at least 2 appear to have a small curve in there spine and I am wondering if this is normal in juvenile fish. I did not notice this when I purchased the fish as they where very small. I have noticed with my other Cory’s that some times they curve there tail up a bit when they are happy after feeding almost like a dog! I have read that fish can get curved from spine from low light and poor diet? The baby Cory’s are in a small 18 inch tank the light is low, but they seam happy. I feed them on a mixture of dried food mainly Tetra prima granuals, and King British Catfish pellets.