I think I found the problem, the stems are covered in aphids. Is there an
easy way to get rid of them?

Michael Shaffer wrote:

My water hyacinths and other plant (not sure what it's called) were
thriving up until a few days ago now I'm noticing the leaves are turning
bright yellow and one is even bown. I know they have enough water (duh)
but what else could be wrong? They were growing fast so I don't think
it's the light.. could I be giving them too much light? I leave it on
24/7 (4 shop lights). I think they have enough food too since I threw
some of those plant tablets in there. I don't see why they're dying all
of a sudden..

Any help would be much appreciated..

Mike