Adding my recent experience with this as a couple also dealing with the same, although a year later. I've let the OP know what we've been through but I also want to post here in the hope it will help others in the future. This has been a frighteningly confusing process with very little information available that seems relevant in recent years.
My fiancee was not asked to do routine testing. We confirmed this through the clinic. Per our blue slip she was not found by the medical psychologist to be a drug abuser. It simply stated she was blocked for a year due to use of a controlled substance. I do not think there is a single process here - certain people may be asked to follow processes like routine testing or not given the finding of the medical staff.
We went back this January (a year after her original failed medical) and it seems all went well. She had to do a full redo of the medical and meet with the psychologist again. It was the same person. She was grilled, again, but she had supporting evidence from her own therapist stating she was clean and healthy (along with a clean drug test from the medical obviously). In the end we got back the sealed packet later that day.
What happened next was a pain - conflicting information and no real way to resolve things without a third trip to the consulate.
Because it had been more than a year, we were denied again based on an incomplete application. We had to pay (again) the DS-160 fee for the K-1 visa and deliver an updated passport photo, letter of intent to marry, updated DS-160 form, a new federal police report, and her passport.
After the second medical (our second trip to Juarez) we went to the info window and were told we could do all of this without coming back to the consulate. This is not true. There was no way to pay the DS-160 a second time via the appointment scheduling website. Eventually I got a response from the consulate via a public inquiry that made it clear we had to go back in person.
We just did this last week and are now waiting to hear back. I would recommend to anyone about to go back for their second medical that they bring all of the paperwork I mentioned above in the hope it will save them a third trip to CDJ. If we'd known, if the guy at the info window had known, we could avoided a 6 week delay and another expensive trip to the wonderful 🤮 city of Juarez.