If they are accustomed to higher alk, then stay there. For nutrients, i am referring to nitrates and phosphates.
So you are at 9.1 and want to be at 10 that is about 56ml of b-ionic part a. Now you do not want to dump it all in at once, we want to check and make sure that we do not over do it, or cause any large changes. So take that and divide by 3 and we will dose it over a 3 hour period. Some will dump it all in, as .9 is not that bad in reality, but I like to take things slow.
So dose 18ml of part a mixed with a little rodi water and let that circulate for an hour. Then test alk. If it came up by about .3 we are good to dose again, the same amount. Then another hour and same thing. Once you get to 10, we know you have a .7 drop in a day. So you will need to dose about 44ml per day to maintain 10.0. This is probably best spread out over the day. For me I use a dosing pump on some tanks. My nano at work gets alk dumped in when i get here and before I leave. Just do not want to shock anything, especially since your stuff just went through a big swing. 22 in the morning and then 22 in the afternoon would probably be fine.
Be sure and test again for the next few days and log it. And then test before doses. This will allow you to make sure the dosing is maintaining it and it keeps from over dosing.