That is pretty normal. When I turned 18 I had to appeal the decision and the state appointed me a lawyer who helped me and my case was reviewed. . .I was able to qualify as an adult. I think it's pretty standard, I mean it's not like you're get better as you get older. It's not hard to prove your still dissabled. I had to do this almost 15 years ago for the SAME reason & it wasnt' too terrible.
*If you get qualified as a dissabled adult and at some point you go to work and earn too much, it will be still be an advantage. I worked full time after I was 20 until I was about 26. When I filed for Social Security Dissability I was automatically qualified I think because I had already fought that battle. . . .Look into appealing it. I think I still got benefits while it was being appealed. FIGHT IT, that's what they are expecting you do so they can requalify you "under the adult guidelines".
Meanwhile, you should qualify for your state's medicaid program if you have little to no income & qualify under their guidlines. Recieving SSI automatically allows you to qualify for medicaid. . .or at least it did for me.
You can also contact the CF assistance program, 888-315-4154 they got me qualified so I can get meds like Tobi, Enzymes, and Cayston (they help with other meds too) I'm post lung transplant so I don't need all the other meds.