Some schools automatically send secondaries as long as you have a primary sent to them. Some have automatic screening to ensure that you meet their minimum GPA/MCAT, etc. Still others manually review and decide whether they will send you a secondary. These could be done in batches once a day, or week, or every two weeks.
Nobody can tell you about each individual school except people involved in the admissions process, and this is not the type of question that I would recommend asking the school about. What I will tell you is that you are early in the process for secondaries, and there’s nothing to worry about. I received my invitations to complete a secondary over the course of around 6 weeks, and all of my schools received my primary at the same time. Prepare yourself for the waiting game, as secondary and interview seasons last for the next 9 months or so. You’ll go crazy if you think too hard about it.
