Thanks for all the responses! Okay, so when I took him too the vet, she took a sample of the skin where it looked to be a tad swollen at the time and put it under the microscope and nothing appeared there, she also took a swab and again nothing appeared. So its a bit odd. They only started off as scratches though... Hence why I think it could be due to the crickets he is eating. He is croaking, very active and is feeding well. I've had these frogs for almost 4 years and had nothing like this until recently. All substances, logs and fake plants have been the same, washed regularly. Maybe another trip to the vet is going to be needed.