The leaves turned yellow because of the algae I think. I've got it on some
parts of my Rotalas from time to time but not major.
People had given up HC becasue of this very algae. I mean it's OK if you can't beat it.
I would try reducing photo period to 5 hrs for a while to see.
ADA use 4-5 hrs for the first 14 days.
And Mark Evans uses 5 hrs for...months perhaps. Have a look at his HC.