(Is) everything OK?
Are you all right? How are you? Said when one suspects that the person being addressed is feeling sad or not their usual self. Everything OK? You seem kind of tense today. A: "Is everything OK?" B: "Oh yeah, everything's fine."
(Is) everything okay?
Inf. How are you?; How are things? John: Hi, Mary. Is everything okay? Mary: Sure. What about you? John: I'm okay. Waiter: Is everything okay? Bill: Yes, it's fine.