Parameters and water changes

ok so i got a mag test kit about a month ago. I noticed my mag was a little low and started dripping supplements into my biocubes to achieve optimal parameters. I know that this should be done with caution, because swinging parameters are not good even if they are heading in the right direction.
So before moving on i will tell you about my tanks. I have a 14gal and 29gal biocube. They both have zoas, palys, rics, and (the 14 has a small favia) and (the 29 has two acans).
My question is with these corals should i even be worried about supplementing? I do 25% water changes weekly with Tropic Marine Pro Reef and have been adding Seachem Advantage Mag and Seachem Reef Builder to my water change water. I am dosing my water change water because when i tested it at a salinity of 1.024 the Alk was 4dkh and the mag was 1225. These being on the low side i figured i would buffer them and get them closer to the reading for Mag and alk in my tanks. Is this a good thing to do? These are expensive and when i run out of the supplements i dont know if i will get more? Especially because i am doing 25% weekly water changes, alot is going down the drain!
So know i am afraid to stop supplementing because of a swing in parameters.
Will this harm my tanks if i just stick to the parameters of the good salt mix or should i keep trying to match my water change water parameters to my tanks? I dont plan on getting any SPS corals any time soon, tried a few in the past and lost them? prolly due to fluctuating params.
Thanks for reading! and any advice will be appreciated

 

honestly with the corals you have, and the water changes you are doing I wouldnt be too concerned. Topic marine pro is great salt and should cover you. Just test to make sure not to big of swing, but I dont suspect you will

 

thanks schackmel,
My Alk in my tanks are around 8dkh and the mag is around 1312.
Should i be concerned if the WC water is Alk 4dkh and mag 1225?

 

alk drop below 6 in my experience causes corals to burn....I would try to get that back up and more stable, mag at 1200 is fine. IMO once you get the kH more stable then the rest will fall in place.

 

The alk in my tanks is 8dkh. The alk in the WC water is reading 4dkh.
Not vice versa.

 

definately add buffer then, sorry!