Are you talking about floating plants? They respond well to be soaked in a bucket with fertilizer in it. Less likely to cause an algae bloom than treating the entire pond.

Some plants always do better planted in dirt such as waterlilies and lotus.

If your plants are nice and green but not growing too much you don't need to add liquid iron (chelated form). I will typically add 1 tablespoon of "stump remover" to our pond once a week which is essentially what you are proposing to do. The stump remover that I buy at Agway (local farm supply store here in the Northeast) is nothing more than potassium nitrate. I've indicated a spreadsheet below that can help you calculate how much to add to your pond. When you go to buy stump remover be sure that it is potassium nitrate. Usually you can check the Material Safety Data Sheet (MSDS) which the store is required to carry or make available on line. This addition should jump start any plants such as hornwort, water lettuce, water hyacinths...any plant that predominately derives its nutrients directly from the water rather than the soil that it is planted in.
Hope this helps.
---David

Here is a link that might be useful: Excel spreadsheet for calculating amount of various chemicals you might want to add to your pond

found some "stump remover" at lowes. according to the msds on the makers website it is 100% potassium nitrate. based on the spreadsheet i'll need about a teaspoon full. i think i'll still add some iron. i have some water lettuce, parrott feather and hyacinths that look pretty ugly and yellow. they seem to have plenty of roots just no growth. thanks for the help. i'll let you know how it works out