okay joking aside it's 1.)memory effect(i did press around 8-9x65/5x70kg some months ago)
but i gotta say im surprised at my fast progress myself, i almost didnt get up 55kg 10days ago and could barely rep it with all my force so i have very well advanced.
IMO the best way to up the weights for one specific exercise is to do it at least 2 times, often 3times a week. you prevent the overtraining through NOT doing any additional exercises like cg bench, incline bench.
i came up with this **** myself because i was thinking for improving i gotta focus on the exercise and do it often but at the same time i have to prevent overtraining so i can only do few sets for the muscle group.
my nutrition was NOWHERE perfect it was everything but perfect, the only thing i did was ****loadz of whey and no booze but i did smoke, fast food, candys and not enough calories.
and the same thing worked good with chin ups as well, and with chinups i had no memory effect.
the only bad thing is that the other exercises seem to drop a bit, next time i will try to not reduce the other exercises so much. i hope i won't overtrain but well you gotta try new stuff to see if it works.
hope this cleared things up for ya silver