CCA performance will always look good after a charge. The meaningful test is what it looks like one day (or more) later because when you park your car at the end of the day it is at least one day later before you restart it.
If you are loosing CCA performance one or more days later you probably have a weak or dead cell. You could also have a low level current draw to some electrical component that beats up the weakest cell.
My bet is it is new battery time. Check out the XS Power and the Optima Yellow Tops. Optima is less expensive. Here is a link to a XS Power stuff supplier who also does alternators =>
XS Power and here is an Optima Listing =>
Optima Scroll to the bottom of the Yellow tops and look at the D31-A.
A good Optima fall back that is comparable to the D31-A but is less expensive and also available with reversed terminals which can be nice on some cars like SPFs is the red top D34 also with 800 CCA.
Ed