Sounds to me like your having a fuel delivery issue in the last 300 ft of the track
I base that on past experiences with fuel delivery, every time we have picked up the 60 ft and 330 times the 1/8 ,1000 and 1/4 mile ET and MPH got better
after fixing the fuel systems
I say that based on the old theory of if you can't slow the MPH down by fattening up the mixture you don't have enough fuel delivery, especially in the 1/4 mile