Could be lots of things. Goldfish will sometimes, not always, nibble new root shoots and the plants just kind of limp along, look bad, black short roots. If you move one plant to it's own container using the same pond water the plant may do well and you'll know it was the fish.

Is your pond in full sun? With the leaves getting brown spots on them so quickly and some drying up it sounds like they got burned by the sun. Water hyacinths like partial to full shade.

Jenny

Oh, yeah they are in Full sun. Thanks

This is just my experience with WH in hot humid coastal Carolina... WH in a 5000 gallon pond, full sun all day grow aggressively, beautifully. WH in a 500 gallon pond, full sun, has a tendency to begin yellowing around about July or so, when it gets hot and stays hot. WH in a 10 gallon water feature, full morning sun, will yellow in just a couple of weeks.

Yes, everyone says that WH likes hot weather but I think water volume plays a huge role in that.

Honestly, for your WH to go bad like that in a days time makes me think they were out of the water for too long a period, maybe? If not, then they went from a shaded location to your full sun pond?

My water hyacinths have always been in full sun with no problems. The only time they dry up is if they have been out of the water too long.

Well I bought them from a pet Store which used lights and such so they put them in a plastic bag. They were in that bag for about twenty five minutes is that too long? Also will they grow back?Or should I try to return them to the store.
Thanks for all the Help!

Well they were in the bag for about 45 minutes and its defently not the two fish since they have only been in there a couple days.

Unlike water lettuce Hyacinths love sun. 45 minutes in a bag in a car in the sun might be the problem. Or in the car with the AC blowing on them could be a problem. Or if they are put in too warm a water the roots can fall off. But 63 degree water shouldn't be a problem. What was the air temperature on Saturday night? A cold night can kill the plant even if the water is warm. I sell a lot of Hyacinths and there are a lot of things that can affect them but not that quickly. So if I had to guess it had to do with the transportation of them and not the store.
Mike

There were 40k winds all sunday so I guess that must of did it. Thanks for the help.

I have had WH be pretty dead looking for months, placed in another container they recovered fast, grew normal, and bloomed. To me they seem to bounce back very fast, like new growth in just a few days.