You have 3 other birds and just brought this one new bird in?My birds are on medicated, so when I got the new girl I fed her the same as them but she was not on medicated feed previously. The breeder I got the first 3 from said it's a must *shrug* I guess everyone has their different opinions.
I would deworm all four birds and I would treat all four birds with Corid if I were you.
From the looks of your first picture that one new bird had a very bad roundworm infestation so no telling what else she is coming to your house with. If she is carrying a strain of coccidia your original three birds are not used to then it could become a problem for them or vice versa.