I did a wild google search and found this:
"Yellowish leaves are a sign of insufficient nutrients in the water; move plants with yellowing leaving to an alternate area and add plant food to their water, rotating with plants left in the pond" ( http://www.liveaquaria.com/product/prod_display.cfm?c=747+892+783&pcatid=783 )
This matches what Sissy said. Does not really make sense when I considered how well they did previously for me in a tub of water. But, maybe something I will try.
"Yellowish leaves are a sign of insufficient nutrients in the water; move plants with yellowing leaving to an alternate area and add plant food to their water, rotating with plants left in the pond" ( http://www.liveaquaria.com/product/prod_display.cfm?c=747+892+783&pcatid=783 )
This matches what Sissy said. Does not really make sense when I considered how well they did previously for me in a tub of water. But, maybe something I will try.