My take would be do you have soda stream? If not regular tonic water should do it, if you do then get rodi carbonate it and dump some in (clean bottle!) Also make sure whatever you do do it slow....
we had covered yesterday how none of the tests you are using are correct in any way but its not your fault, this happens to all new reefers that use only api and not the brands reviewed below for you yesterday.
the difference between light purple and dark purple could be 200x impact difference on the pH scale, which is why we cant use api to make reasonable inferences about true pH. but to save all detailing in the future, no API testing can be used to manage your tank or make changes to it accurately.
just knowing that your whole tank would be dead if it was 8.8 should stop all API concerns going forward...but even if not, its ok that's what all purchasers of API must go through until guessing is no longer good enough for the investment.