If the beds are mostly old compost, I would just add the amount of compost and manure needed to top it off. The older stuff is still breaking down and releasing nutrients, and will also provide a matrix to recapture some of the more volatile nutrients released by decomposing manure. If you have just an inch or two of room, that is plenty of fresh compost to add each year to refresh the nutrients in the soil.

If you initially filled the beds with a significant of materials that were not parts of Mel's mix, on a one-time basis you may need to replace enough of what is in there to get with of the sand / silt component so what if left all breaks down enough each your to just top off with an inch or two of new compost.

Let me explain, the soil is at the top. There in no room to add more soil unless I take something out.

Could you use that to start anew bed?

I was gonna suggest a new bed too? lol

Do you have a compost pile you could add it to?