Hello!
Your question is, unfortunately, not easily answered. For one thing rooted, floating plants need a different fertilizing regimen than potted plants. The Eichhornia ( water hyacinth ) might benefit from an application of a soluble fertilizer, like Miracle-Gro 20-20-20, cut to half strength. For potted plants, I now suggest a time released product made by Florikan and widely sold in stores as Dynamite time release. It was developed for aquatic applications and while not as easily applied as say a tablet, the effort required is minimal compared to the expected benefits.
The problem with a specific answer is you do not mention water temps....hyacinth are tropical and evolved to survive in warm water and twelve hours of strong sunlight. You do not mention water temp, but six hours seems insufficient light and even given sufficient light, they will struggle at water temps much below 70. . As for the dwarf lotus, if it is a Nelumbo and not the waterlily (Nymphaea ) sometimes sold as 'tiger lotus'....and it has a tuber, it is evolved to go dormant when day lengths shorten, and six hours is short. If it has a tuber, I suggest you do not worry about fertilizing and move it to a location that will be cool ( 40 degrees or so ) but not subjected to freezing temperatures....a basement or attached garage for example....so it can enter the natural period of dormancy.
Truth is not what you want it to be; it is what it is. And you must bend to its power or live a lie.”― Miyamoto Musashi
"Knowledge speaks, but wisdom listens." ~ Jimi Hendrix
“The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge.”― Stephen Hawking
Craig