Originally Posted by Tom Barr

Yes, 2x and recommended dosing and 2x and frequency of dosing is a perhaps a good reasons based on what you have told us here.

They do suggest the dosing rates for a reason
You have CO2, so do not bother with Excel.

Other things are more general, always do a large water change after you do any large changes, pruning etc, do not wait a couple of days etc.
Clean filters often, make sure you do more water changes, check the Tap water etc.

Regards,
Tom Barr