Internode distance and FIM

hey guys, so I’m about 2 1/2 - 3 weeks into my plants and I’ve got a few questions
When can FIM come into play? My plants are getting to a bigger size and I just needed to know when exactly I can start this procedure.
I also really wanted to know if I have the right amount of internode spacing, because I see a lot of leaves growing where they can’t get light in between my nodes.
Here’s a couple pictures

Any time after they start throwing regular leaf sets. Same with topping.

hotrodharley said:

Any time after they start throwing regular leaf sets. Same with topping.

Click to expand...

Regular leaf being the marijuana leaf? It’s had a few nodes of that already