You need to know your daily tank comsumption and dose ever day accordingly. You deffinelty can not do one big dose in a week. That explain Your alkinity are all over the place. That is alk swing. Very bad for SPS.
LPS can handle the dip. Your SPS looks fine for now. You will see the result in a month or so... SPS will suffer.
First Dose alk solution only, to bring your alk back in line. AND keep it in line. Choose a dkh number and try to stay in range from day to day. Now dose alk only and DO IT VERY VERY SLOWLY! Rush it and you will cause STN or RTN on SPS. Do not dose cal, don?t worry about calcium for now. But do test mag and cal weekly to make sure they don?t drop out of range.
Best low cost way is to get a doser and dose klakwasser. Klakwasser are equal part of alk and cal. Jabeo 4head doser is 75.00 on amazon. I have good luck with it. I use 5 gallon bucket of klakwasser solution next to the tank. I was dosing 1500ml of solution per day. I program the doser to dose 100ml every hour for 15hrs when the lights are off. There is and will be a limit of Kalk dosing amount by your daily water evaporation. If you dose two parts than you need less but do spread them out. Try not to dose whole days worth of alk at one time. Stablility is key.
People recommend dosing Kalk in
ATO. I do not recommend this if you have a valve to control your return water level. Trust me! I change my return gate valve setting. The water level rise in display tank slowly over 12hrs. I came home to a tank that I can?t see 2? pass the glass! My water level rise in display tank by emptying the Sump, the ato think my sump evaparated so keep dumping Kalk into sump. It OD my Tank.
Owning a reef tank. You will need to do water change. No way around it. You are only dosing major elements. Minor element are used up. You must replenish major and minor elements.
Now calcium reactors. Calcium reactor will replenish major and minor trace Elements. It is dose ever second, every minute 24/7 = stability. Best of all the options but cost the most upfront. Long run is cheapest for large tanks. Even with cacium reactor you will still need to do water change to get rid of waste and toxins in the water. You can get away with less water change.
I have aquarium since 90s. From fresh water to saltwater to fresh and now back to salt water. Never have a tank I don?t do water change every week or 2.
Feel free to pm me if you need so,e advice.