HELP!!! For 3 months, hen hasn't stopped laying thin shell or no shell egg....HELP!!!

[silkieloverz123]

my hen gets oyster shells,grit, and egg shells in her diet but she has been sneezing really bad so i brought her in and quarantined. her and she layed an egg and it was busted open and the egg shell was not a shell.it felt like a latex balloon. thats a new one for us. im assuming its cause shes sick. i hope it clears up. i medicated her with sulmet. I guess now we wait.