Quarantine it from the others if you believe to be sick. This will make monitoring it easier and how much it's eating. Use paper towels as substrate and make sure faeces are hard and not runny. If there's still crickets running about in this set up and it starts to lose weight then I'd think about force feeding but you wanna be 100% sure that it needs it as it will stress it out. What are your temps, humidity, lighting?