I really like this set of elements. I have them dosed from my dosing pump and I test semi-regularly for all 4.
I found that by keeping up concentrations of all 4, I was able to go without water changes for quite some time [4 months on a ±10 gallon SPS tank], quite similar to the DSR method, and this seems like a great all in one to negate the depletion from growing and metabolic processes. It is very important you test for all 4 as they are easily overdosed, but I do notice a decline in coral colour if I don't refresh my dosing containers soon enough.
These 4 bottles essentially contain the 'trace elements' that we rely on regular routine water changes to replenish, and they are usable in a way that allows you to tinker and adjust colours if you so wish, it does still require a good nutrient balance and won't help if your tank is in a state of nitrate limitation or excess