It's pretty common for beginners and even mid-level honers to lose sharpness as they move up in grit.

There is a huge mental shift that has to occur between 4K and 8K. Once you get to 8K you have to treat the blade edge like a butterfly, letting it touch down gently on the stone. You have to move the razor without pressure, so each stroke on both sides will be equal in pressure (using the weight of the blade as the equally factor). You have to hold your pinky under the scale so the edge remains consistently flat as you move the razor across the hone without lifting.

You need to replicate each stroke, in angle, and distance on the hone on each side. So, the razor, when it moves toward you should be a mirror reflection of what the razor looked like when going the other direction.

The key, though, is a light touch.

When you hone of 4K you can make all kinds of simple mistakes and poor strokes. Your really only aiming for a consistently sharp bevel. Like if you were honing a knife, childsplay really. Setting a bevel is a pretty simple act. It does require you pay attention to ensuring that you are getting a consistent honing across the entire bevel and shooting for sharpness, but, given the proper attention, isn't too hard, skill wise.

Pastes are good after finishing stone actions. I would work on perfecting your 8K strokes and them moving up from there.