Water parameters were fine EXCEPT the Ph. It was barely 8.0...looks more like 7.9
So, I have followed the directions and added some buffer.
I wish they looked as nice as yours do, melosu. I have 5 heads, the two original larger ones, and three new 'babies'. The color has gone from the centers, from the nice green like yours to just plain brown (like the stems). One of the large ones appears to have turned inside out like a little ball for nearly two weeks now. The other large one has lost the hair around the edges, but still opens and closes like normal.
I will relocate them to an area of lesser current and get the Ph back on track.