Why when I water some of the pots it seems the waters runs right through it. The runoff happens so fast.

Mine do that as well, I assume the root growth was faster then others and created more open channels for water to run through quicker. You're probably going to find those that do that also get more air and need watered more frequently.

If you water slowly it'll help prevent that. When the soil is bone dry it goes through more than if the medium was still a little moist.