Very simple stick-figure rigging

I have a very simple 2d stick-figure rigging. One bone controls the head, bone1 controls the torso etc.!
The stick-figure has been weight painted using Shift-K so that for example bone1 has head vertex to weight 1 (red) and the rest completely blue (weight 0).
But when I bend the torso there is stretching in the legs (see image). What should I do to prevent that?
Image4|689x308

If I see that correctly each limb is its own standalone mesh. If that is the case you can skip the entire weightpainting/armature modifier part and just parent the limbs directly to the bones.

Thanks for the reply.
I’ll try that but why are bones affecting other parts of the mest although I’ve set weight to zero?
[Edit]
I found a solution from: https://blender.stackexchange.com/questions/137436/mesh-deforming-when-weight-paint-is-at-zero