Hi Nick,
CP's are, for the most part, slow growers. This is because they grow
in soil very low in nutrient. Using 1/4 to 1/3 normal strength
plant food (fertilizer) will get them growing alot faster and in a
healthier way. I use to use the yeast method also and it does seem
to work but you end up plants that go in to withdrawl and stop growing
when CO2 stops being feed to them. Of course, you could stop feeding
it to them in the fall...
Dave Evans