Talk to your attorney. You are responsible for these post petition debts. You are generally not allowed to go into debt while in a bankruptcy, but there is an exception for medical debts. Depending on how much they are and what the structure is for your plan you may be able to add them to the plan with the consent of the creditor and trustee.
Generally, your disposable income is considered an asset of your bankruptcy estate necessary for the functioning of your bankruptcy plan. The creditor may have to get relief from the bankruptcy court to pursue collection actions against you, but not a judgment (you are not protected from post-petition debts). You can always contact the creditor and try to work something out. Otherwise, the creditor will have to wait to get paid.
If you have an attorney, talk to the attorney to find out whether anything can be done. Maybe it is an ongoing medical issue that unexpectedly changes your expenses possibly leading to reduced Chapter 13 payments. It all depends on the specifics of your situation.
[This communication is intended as general information and not specific legal advice, and this communication does not create an attorney-client relationship.]
Debts incurred after a bankruptcy case is filed are not generally subject to being discharged. However, as you have incurred medical expenses that you can't pay with your current budget, you should explore the possibility of modifying your Chapter 13 plan. It may be possible to adjust your payments to give you room in your budget to pay the medical expenses.
You need to consult an attorney. Modifying a Chapter 13 plan is not easy to do on your own.