At first I just thought they were poorly designed and didn't fit together very well. Then I got to one that didn't fit together at all without some major cutting, and it left a huge gap between the pieces. Then I realized that I was trying to fit two parts together that didn't match, but I had already glued the others together and couldn't get them back apart. So I was stuck with the bad fits. So if you're going to assemble these, do it one at a time and pay attention to the numbers next to the pieces on the sprue.
So with that warning out of the way, below are the 5 Termagants I painted up to try and work out my color scheme for the other Tyranids I will be painting in the near future. As I talked about previously, part of my concept is that younger organisms are lighter in color, and older ones are darker. I imagine the weapon symbiotes don't survive as long and need to be replaced more often, so I made the Fleshborers a lighter color (pink) than the Termangants carrying them (red). Previously, I had made the weapon symbiotes more of a light orange color. I'm not sure which I like better. I'm hoping to refine my color scheme and methods before I start painting the bulk of my remaining Tyranid stuff, so let me know what you think.