hey bill, it looks to me that your snapper is just shedding on the plastron pic. as for the lines on its lets that could just be some nice coloring. i have three of them and depending on how much sunlight and or uvb lighting they get and also depending on how warm i keep them they go from a dull dark brown to extreamely light brown with some amazing colors in them. as for the tail however this is just a guess but, i would also attribute that to growth and shedding. keeping in mind these are just observations and opinions. hope that i helped.