I have/had the same issue on an Anet A8, using OctoPrint with the plugin.
I think I have solved it by editing the printer setup in AstroPrint, go to advanced settings and in the End Command add:
M104 S0 ;Extruder temp 0
M140 S0 ;Bed temp 0
Not entirely sure that this works as it should, since I’m doing the first print since I did the change right now.
Can write an update in the morning.