To keep things simple let just look at your Alkalinity at 9.5.
People dose to maintain an Alk of 9.5 in their water. As the corals happily absorb the light during the daylight hours they do their thing growing and building a calcium based skeleton. And that hard skeleton comes from pulling the calcium and alkalinity out of the water column.
When you take your water sample your grabbing a random sample of 10ml of water and testing it to find out your Alk is 9.5.
So all the water in your tank/system is 9.5 alk - all 25 gallons.
Now the corals as they grow are pulling from that 25g volume. Look at the size of your tank and size of your 3 frags and then realize that the coral is only growing, in your case encrusting most likely, around the base of the coral for the most part and realize how much alkalinity it was to pull out to make that 25gallons of water drop from 9.5 to 9.45.
Dosing is to maintain that 9.5 as stable as possible.
With your weekly water changes, and 3 frags I doubt you well see the alkalinity drop outside the margin of error for the accuracy of your testing method. You just don't have enough consumption, yet.
Two summers ago when my 1350g system was packed, during the daylight hours the system was dropping .5dkh per hour - This was determined by having an Alktatronic test every hour 24x a day.
With that kind of data you could see the Alk start to drop as the sun comes up in the morning. You could also watch the pH rise as the sun gets stronger throughout the day.
We run both a Giant Dastaco Calcium Rx for dosing and a Kalkwasser Rx. All of our top off is Kalkwasser, which on a hot summer day when Alk is dropping .5 dkh per hour (that's while the Calcium Rx is cranking too) we replace up to 75g a day in Kalkwasser.
During the night the Alkalinity consumption drops off so much that we have to shut the Calicum Rx off during the wee hours.
We had literrally 100's of lbs worth of coral colonies that was consuming this much alk. With just 3 small frags your amount of biomass of coral consuming alkalinity is not enough to drop the alk if you are doing your regular water changes.
You have a while to go before you need to worry about keeping up with dosing.
Dave B