I agree with what others already said here.
I would avoid broccoli, but an "occasional" feeding won't hurt (I give mine some broccoli about once every 6 months...this would include the leaves you mentioned).
If they hate the lettuce, try something called "collards." These are dark leafy greens that many of them love.
Pond plants (like anacharis) are a big hit with RES's too! They love to shred the leaves & eat eat eat it. Makes a big mess, but they LOVE it & will clean it up if you just leave it in the tank.
