What was the decrease in approach speed of the KFIR over the Mirage 5 due to the canards?
The KFIR has similar airspeed specs as the Mirage 5. However, I'm not clear on what you mean by "Approach Speed". 

Approach and Landing Phase:


Vectoring Speed: 220-250 kts
Max Gear Speed: 270kts
Approach Speed: 190-200 kts
Touchdown Speed: 170-180kts


Source