Other plants in substrate?

[Rwise]

1 I have no idea
2 Because the conditions are right for them
3 IDK
4 I would remove them

[Beginnersprouter]

Heya so I'm trying a different substrate for the first time, it's canna professional Coco coir, mixed with perlite at about a 65-35 ratio, I've come to check on my girls today and noticed there's some new little sprouts in the substrate!

I'm just wondering if:
1. You know what these plants are?
2. Why are these plants sprouting?
3. Would they be at all harmful to my cannabis plant or the rooting structure?
4. Should I remove these plants?

Thank you for all the help In advance you're awesome!