Hi,

You did not say which version of audio cleaning lab you are using but if you have version 17, the answer is that you can to it either one at a time or for the whole project.  You may also want to first try the "Cleaning Wizard" instead of just one filter.  It may give you a better overall result than just using the Declicker.

This from the version 17 user guide

Declicker/Decrackler
The Declicker efficiently eliminates any crackling and clicking they are typical in scratched LPs.
This function can be very efficiently used in the "Object clicking sounds are not present on a whole, but just in some First, you will have to find the damaged areas using the you've found a damaged area, make a cut in front of it and after it using the  scissors-tool, so that you obtain an independent object.
Activate the "Object FX" button of the small object, so that the declicker will only be applied on the area with the clicking sound.
Marker Declicker
Alongside normal crackling on a vinyl recording, there can noticeable ones on a record which is scratched. If the DeClicker for those sections which are particularly distorted, then several components of the desired signal will be treated they exhibit similar characteristics of the distortions.
To avoid this we recommend setting the DeClicker at a removing the sharper pops/clicks with the help of the "Marker These sections can be set using a click marker (Set click special "Marker DeClicker" affects the audio material (when these positions, and the normal DeClicker can be used material.
"Search clicks" allows you to search the entire project for clicks and have them marked automatically. With the "Sensitivity" you can set the sensitivity of the search, i.e. the higher clicks will be found (according to intensity).
Especially strong clicks and audio disturbances can be Spectral cleaning (view page 85) (deluxe version only!)

George