The addition of organic matter of any form will do two (2) things;
1. It WILL increase the CO2 levels. Only this increase will be evident during the entire diel cycle, It will not only lower the high (PM) pH levels but also the AM levels. You will still have the same differential in test readings. You want to ideally keep the pH range between 6.5 and 8.5. This has been determined to be the most suitable range for most aquatic organisms.
2. The bacterial action on this additional organic matter may result in a severe drop in DO levels as the bacteria utilize Oxygen in the breakdown process; CO2 being the by-product.
Ag lime is still you best course of action given the info that you have posted.
As you have stated, a decrease of .5 will lower both the am and pm pH to the parameters you suggest as ideal. I have good aereation 24/7 to keep O2 levels acceptable, seems like a little drop in over all ph is safer than changing the natural alkalinity
