Ok! now it makes perfectly sense!
100 drones? WOW
So, is the issue solved?
You disabled the autoconnect feature of QGC and connected manually?
Anyway, adapting the px4-rc.mavlink is a good way to tune your system.
Another approach could be to set up
You could use 4 instences of mavlink router to collect 25 drones each and then interface each interface on a different QGC instance