Since you have other tanks can you move your corals to those other tanks and then put this one through a no photo period like for a week?
I think that along with some good RO/DI water changes will alleviate your problem.
And just for the record, testing your water in the tank when you are having an algae problem is completely pointless. The algae is going to be using the nutrients in the water in order to sustain themselves. Thats why when you see people posting things about LHA or other algae outbreaks 99% of the time their parameters are wonderful. You need to have your input water tested period.
Algae will not grow without the presence of three things. Light, Phosphates and Nitrates. The easiest to eliminate is phosphates through the use of RO/DI water.
You have stated before that you have tested your input water for phosphates and didn't find anything, and I'm not saying this to be mean or hurt your feelings but I find that hard to believe. You use well water, or at least thats what you stated several posts ago, and are the first person I have ever heard of that doesn't have phosphates in their well water.
Using whatever your LPS gave you is only a bandaid to your problem. While I strongly believe that it is the water from your Rots that contaminated your system algae once in a system will continue to grow until you eliminate one of the things they need to survive.