Why are my floating aquarium plants deteriorating?

[Clack]

If you're not fertilizing, that's probably the issue

Not sure what you're getting at

[velvet8]

If you're not fertilizing, that's probably the issue

You're overdoing it with the Flourish.
5ml for 250 liters, once a week, that's what Seachem says.
You're using 1ml for 5 gallons, 1-2 times a week, that's a huge overdose.