How do I unroot my tablet, as well as replace the custom with stock?

Okay, I have a Samsung Galaxy Tab 4 7.0 Wifi. I ROOTED it using Kingroot. I did unroot using the kingroot, yet even though RootChecker says it is not rooted, in my settings about phone, it still says custom, and I cant update firmware. So I re rooted it with Kingroot. How do I unroot this, and get the custom to the stock? And, furthermore, can I do this without a PC? Also, I have not done any flashing or custom, just downloaded apps to boost my cpu.