Forgot to mention he is growing very well and seems healthy in every way. Also, as to the red coloration, this was only during summer when I was feeding him wild grasshoppers.
Can it be that the claws on their legs and or their mandibles are causing him grief during the process of eating and digestion? He might've been too young then to feed adult hoppers, but they did fit in his mouth, so I thought he'd be fine. I made sure to collect prey in chemical free areas. If that helps anybody to understand the situation!