Algae does release leechates like dissolved organic carbon, simple sugars, etc. which isn't really a big deal. Carbon dosing you are doing the same thing. That being said though if you have caulerpa growing right next to a coral you will see it damaging the coral. Alage fights with neighbors just like anything else on a reef. Green and red algae have differences in what they release and uptake as well. If your algae was a brown algae it was actually a form of red algae. Red algaes uses up more iodine then green as well so you could have been iodine deficient. The video I am linking will break down the differences of their effects more and was done by Julian Sprung himself. Algae also uses up more nutrients than just nitrate and phosphate so when you don't trim it and grow too big for your system it can be pulling out things you will have to dose for to keep everything in balance.. or just keep it trimmed smaller when it gets to that point or reduce its lighting photoperiod. For any sized system there is such thing as too little or too big with algal filtration but like I said they can be tuned via trimming/photoperiod and benefited by water changes for replenishing what is lacking. Dosing for replenishment is also an answer but, in my opinion, that is annoying and I would rather tune my algal filtration down to the point where a regular water change replenishes what I need.. or get to the point where just dosing some iron is all that is needed rather than dosing a cocktail of things like contained in products like brightwells chaetogro. It sounds to me like your algal filtration was too this point in your system. I can't comment on the NSW from scripps. Plenty of people use it with success. I would always rather make my own though so I can be assured I am not releasing some disease like ich or some contaminant unintentionally. Julian Sprung did an interview going deep about algal filtration that is definately worth the watch.
