I can give some advice but first I have a few questions so I know the proper advice to give. Answer as many and a thoroughly as you can to get a better responce.
How long have you been trying to feed it rats?
How many times have you tried?
How often do you try?
Try to rememeber what method you used each time and tell me in order what you have tried. And how many times you tried each method.
What is your normal feeding method for them?
When you say you feed 8 mice is that each or total for both of them?
What size rat are you trying to feed them?
Is it live or frozen thawed rats? Also what were the mice?
Can you post a current pic to show how big they both are? Something in it to make reference of size will really help too, like a pop can or quarter or pen or something common like that.
What time of day do you feed them?
How was their feeding responce before trying rats? Awesome, eatting every time? Good ate pretty much every time but sometimes skipped a meal? Poor sometimes ate, sometimes didn't?
Do the snakes still appear healthy right now? Any sign of any sickness or illness.
JCP's are very good eatter so unlike some snakes it can be a lot easier to switch them over but sometimes you can get ones that can be difficult. That fact that you are having trouble with two of them makes me think part if it could be you are doing something in your methods that could be hindering them. Don't take offence to that please I am just stating it to try and help. And it might not be you, it could just be a coincidence you go 2 difficult switchers. Age can sometimes be a factor. The older a snake is the tougher it can be but if yours are only 2 years that shouldn't factor in much.