What does it mean when tomato hornworms cant shed out of their own skin?

Well I have three questions actually. I want to know why my tomato hornworm is more wrinkled than the other ones, why can't the same tomato hornworm shed out of its own skin, and why is still the same tomato hornworm not growing and is smaller than the other ones? Can anybody help me please?

Hornworms are a very easy species to rear. As long as you keep them fed consistently, your worms will reach their adult size of 3-4” within 2 weeks. You can speed their growth by increasing the ambient temperature of their container to around 80 degrees (Do not exceed 90 degrees). Consequently, you can also reduce their temperature to 60 degrees (Not below 55 degrees). Do not refrigerate your worms without knowing how cold your refrigerator is, as they are commonly well below 55 degrees Fahrenheit.The key to keeping your Hornworms healthy and nutritious is emptying their droppings regularly and making sure they have high quality food at all times. You might notice that your hornworms will commonly resemble the color of the food they are eating. For example, if you feed your hornworms Mulberry chow mix, commonly used when raising silkworms, your worms will be a dark green color, and when you feed them Wheat Germ based chow mix, sold by most hornworm suppliers, your worms will have a much lighter green, almost blue color. Careful when substituting the traditional wheat germ based mix with Mulberry mix as your worms will have to eat more food (and produce more droppings) to gain the same size at a much slower rate than the Wheat Germ mix.