Probably because the feedforward layout doesn't currently account well for the size of the text labels. When the layout pane is small, the network is displayed small because a zoom-centre is performed. Then since the sizes of the labels don't change, the javascript engine will render it significantly differently than the feedforward layout expects.
Hmmm... I'd be somewhat tempted to just get rid of the automatic width change due to the size of the text labels. Especially when those networks are so small that the text dominates everything else.
Probably because the feedforward layout doesn't currently account well for the size of the text labels. When the layout pane is small, the network is displayed small because a zoom-centre is performed. Then since the sizes of the labels don't change, the javascript engine will render it significantly differently than the feedforward layout expects.