Problem with larger Tarantulas?

I can't seem to get my larger tarantulas' (7+ inches) abdomens bigger. In other words, my tarantulas look unhealthy because their abdomens are too small for there size. I have tried:
Feeding More Crickets
Feeding Wax worms to fatten up
Larger Waterdishes
Keeping the substrate more moist/raising the humidity levels
I can not feed them roaches or another large insect because they don't sell them around here; just crickets
What can I do to make their abdomens larger like other people's spiders?
Answers:
Beef up what you feed to the tarantulas. What goes in those insects will eventually go in your tarantula, after all! You can look up the diets of the insects you feed using wikipedia.org or google. Crickets are omnivores and will enjoy a variety of foods (they love dog food, cut grapes, lettuce, very small scraps of meat etc.) You can also purchase cricket food. (There is a brand called Flukers. Buy it at PetsMart or Petco. Flukers also has special, gelatinized water for feeder insects. It's so they won't drown.) I know all this because I own two treefrogs and their main diet is crickets. (my white's treefrog, when he gets big enough, could even eat a small pinkie! Both frogs like minnows, as well.) I used to work at PetsMart, read extensively, and volunteer at the Dallas Zoo. (please don't think me arrogant. I just want you to know that I know what I'm talking about) In addition many larger tarantulas will eat pinkie mice and possibly small fish (like a guppy or a minnow). If availabe anywhere, you can also feed them very young baby birds (use domesticated ones) that still have their yolk sac. The yolk will fatten up the spider (hopefully) and will likely add a healthy sheen to the spiders' hairs.