This is a report on my efforts to help my small browning hyacinth.
One of two berm ponds had really stunted hyacinth, that never got tall
(3") The other pond had hyacinth that have become modestly tall
(12"). Both had really yellow plants. The hyacinth in the short-
plant pond have largely died out or stayed small with increasingly
brown leaves. The water celery, on the other hand, has continued to
thrive, and has the parrot's feather.

I added potash and saw, perhaps, some response in green veining of the
leaves.

I added iron relatively soon after the potash, with the result of more
greening of the hyacinth and some fully dark green leaves on new
growth.

I am wondering if I got some sort of bug on the plants. Both berm
ponds have the same water flowing through them. One got tall, the
other stayed small and the leaves have browned by the edges.
Something is different between the ponds. It has to be on the plants
rather than in the water.

With respect to the color of the plants, I have never had them stay
yellow like this.

One other thing, The water in the pond is more clear than it has ever
been and the blanket weed has done its usual by thriving in the berm
ponds (No koi) and never getting a foothold in the main pond.

My analysis: Some sort of on-the-plant disease or critter in one berm
pond and a general lack of some mineral that resulthed in the yellow
leaves. The l;ack seems specific to the hyacinth.

Jim