The medical collection shouldn't be an issue for FHA or USDA loan. However, medical collections are generally the easiest to get removed. The CC charge off can be an issue for a couple of reasons. The balance is likely reflecting an over 100% utilization which means it's hurting the mortgage scores significantly. This can in turn affect the rates your offered and can affect your DTI ratios. I would take care of the CC charge off first as it has the most impact on your overal profile. How long ago was the CC charge off and the CC lates? These both must be at least 12 months ago as approval with anything more recent is rare.
There are a lot of posts in the credit building forum about pay for delete. In the simpliest form you call up the debt collector or whoever is now reporting the debt, negotiate a sum of money you will pay to settle (or pay in full). You will then ask them to remove from your credit report in exchange for payment. If they agree, get this in writing before making the payment. Keep in mind some CC companies will refuse to do this, I had this issue with Merrick Bank and First Premier Bank.
In February you didn't have a recent late CC payment. If you were 120 days late last month, that means you started being late 3 months ago. If you lookup FHA/USDA guidelines you will see it is pretty clear in no late payments in the last 12 months.
USDA can be a little more strict... But when it comes to FHA, when you look up the information online, it may tell you you cannot have any late payments in past 12 months and will also tell you that the max debt ratio is 31/43 which caps you at a 43% debt ratio... But, that is for most (not all) lenders MANUAL underwriting guidelines.
When working with a lender (who has no overlays) if you receive an AUTOMATED approve eligible, this will over ride those manual guidelines.... I personally close FHA loans with multiple lates within past 12 months and the max allowable debt ratio is 56.99%. instead of 43%... This is just 2 example of many. Lots of people (including loan officers) do not know this information but we have been reviving and closing these loans after buyers have been turned down by multiple lenders. Plus, there are no hits or increases to the interest rate. It is all credit score driven.