I don't know if this would be safe but I'd suggest taking the valve core out, filling the tube with water, and seeing if water is leaking out. You could also take out the tube, inflate it to around 10 psi or until it get somewhat fat( just don't explode it) and pouring water around the tube. Any leaks will appear instantly. If you don't find any holes, replace the tubes and get some with the green slime.