P015, I don't think it's been tried specifically against that, though it seems effective against darn near everything.
It sounds like your plants are languishing. Growing slow. Old leaves with algae accumulating over time, and winning as the leaves' protective layer degrades. Plants not able to keep algae down in the tank as a whole. I'd definitely dose at least some minimal, but comprehensive ferts, and perk the plants up.
Despite having developed a technique which someone recently described to me as "nuking the algae from orbit" (love it!), I do often prefer to solve problems using minimal force. In your case, I'm sure it could be turned around by solving the underlying issue. Some manual cleaning, since it's easily removed algae, unlike many discussed here. Growing and trimming plants. Plus maybe a cleanup crew, many species eat soft algae. Ramshorns and otos love it, and cherries will probably enjoy munching on it too. Success is measured in weeks not days, but it will come just the same.
So that's my recommendation. The choice is up to you, of course. I do appreciate you have a window of opportunity to rapidly clear the algae, which closes when the shrimp arrive, and you may want to take advantage of. But you will still have to solve the underlying issue. If you don't, or if another issue appears, the algae will return and you'll no longer be able to safely use the One-Two. Better to use this as an immediate opportunity to practice and gain experience from turning a tank around using less intrusive techniques, IMO.