Stainless Steel & Floaters

Couple questions: One, I put some bog and floating plants in a stainless
steel barrel outside in the backyard with a powerhead for circulation. I've
added Chelated Iron and trace elements. Plant growth is good on the floaters
(Water Hyacinth, Limnobium, Pistia stratiotes), leaves are strong, and well
formed, but all the new leaves are coming out bright yellow. They get a few
hours of direct sun per day. Is using a stainless steel barrel a bad idea, or
do the plants maybe need even more iron? I added a pretty generous dose.

My other question: In my plant tank, my Nymphoides aquatica and Nymphaea
"Tiger Lotus" are now putting out mainly floating leaves. It was cute at
first, but they're now blocking serious amounts of light. How should I handle
this? Just cut off the floating leaves?

Thanks in advance for advice.

Kent Elliston