Trust your instincts. You know your cats. When my Coco Puff's meow changed, I knew something wasn't right. That's when he went deaf due to a sinus infection. He regained most of his hearing, thankfully, but I knew he wasn't right. If I recall correctly, I think I posted that his meow had changed. Call your vet and maybe s/he can reassure you w/out an appt. but, if not, have them checked out. Since they both seem to have laryngitis, it may be something that they'll continue to pass back and forth between them and a vet visit might be able to clear it up.