Transistor turns off only after a delay
You are seeing the Miller capacitance holding the base on for an extra 1.5us or so. It's caused by the capacitance between the collector and base of Q3.
There will be a similar effect on the base of Q2.
If you need faster switching, replace NPN with 2N7002 and PNP with BSS84 and reduce R4 to 1K and R3/R5 to 100 ohms or 0.