Slow grow or no grow

I am down to 120 tarantulas (not for long) and have had tarantulas for over 12 years, so this is not a newbie question. Specifically, my E. weijenbergi and L. polycuspulatus seem to simply exist and nothing more. They seldom eat. They don't molt or grow (one molt apiece in over a year). They seem plenty active and in good health, but in comparison my A. bicoloratum and other desert species are growing like weeds. Can anyone offer any specific husbandry suggestions? I know patience is a virtue, but I've never been accused of being all that virtuous.

I don't know anything about L. polycuspulatus but I got tiny E. weijenbergi slings a long time ago and my feeling is they will not be moved out of the same tiny cube they are living in, in my lifetime.