I don't know what's easier, mastering advance physics or making you understand how basic things work.
12873 reached ANVT late, so 12874 was given a late departure due to less TAT. It's again out of slot by 1.5 hours or so. At this time of night there is a high traffic of trains leaving Delhi with designated running slots.
Above...
more... that, all the trains you've mentioned are running on time and they're all SF category, the same as Swarn Jayanti. Is there any logical reason to detain and delay them, too, just because YOU want a certain train to be prioritised.