to my understanding you don't need to dose amino acids if you are not running the special system like Ultralith, Zeovit etc. since ultralith, zeovit systems will strip everything out from the water and you have to dose amino acid to replace the stripped ones, so you can have more control of what the corals are uptaking. but if you are running regular systems, water changes and feeding should be enough.
I am running ultralith and I have notice if I forgot to dose the amino acids the SPS will turn a lighter color, but if I up the dosage, the color becomes more vibrant. but if I dose even more, there will be a lot of film algae starting to appear everywhere. that's my experience.