Budgie Very Thin Feather Problem - Has Anyone Seen This Before?

Hi All,

I bought my a male budgie from a pet store and he appears to have a feather problem, behind his neck and on the vent "butt" where there is no feather "bold" and the feather on his body looks very thin i can feel the meat/bones when i touch his head or belly and the weird thing that his size looks very small and short tail and the bars on his head still there but his eye has a clear grey iris, something like it's old but still small in size,  so i'm not sure can you please help me?