My 10 year old NC321 has been treated with Semco since new and I think it is very good except rather expensive.
However in my experience the dirt builds up in the wood and the algae starts growing again so that after every 2 years or so I have to go through the whole cleaning process again.
I wouldn’t get rid of your excess cleaners because you may need them in the future. To save a bit of money I have also used the 2 part cleaners which are sold by Compass24 mail order under their Teak Wonder brand. I have also tried their Sealer but it is not as good as Semco.
As far as I can see the cleaners are an alkali solution and the brightener is an acid solution.