Had a small crash today, only 3 ft off the ground, ran in to me. I tried to move but im to slow and it flipped upside down and broke one of the props. I replaced it but would it be a good idea to replace the other 3? Only scratches on the painted centers.

I wouldn't. After a while flying these things, you will end up with a lot of extras. I mix and match all the time and everything works just fine.
I however, am not looking for professional quality video and some guys are nutty about their props. They have gizmos that show if a blade is out of balance and then lightly sand one side or the other until they are balanced.
If you need that, then replace the other 3. But if you just like flying for fun, don't worry about it - your drone won't fall out of the sky.

I do check balance as an out of balance prop can increase power draw on that motor. It also reduces vibration ...

I haven't broken a prop yet and still using the same 4 I fitted ages ago when I first got the P3. Its had some scrapes and 'events' but they are still flying her. I do look them over and give a wipe down with damp cloth to see if any damage. If there's a small nick in an edge - I'll 'dress it' and then balance.

If I broke a prop and other 3 were OK - I would just replace the one but I know others who religiously replace all 4 in  belief that if one is damaged - other 3 may have hidden defects. Lets be honest - they are not expensive !

Nigel