That being said, it's excellent stuff for low-maintenance setups. It's hardy and eats pollution like no one's business. You'll have to remove it manually every week so that it doesn't kill everything below it via nutrient deficiency but you'll never have a detectable ppm of nitrogen with that...
You stated you change your lighting, your plants will probably require more nutrients. When I have backed off adding ferts my elodea seems to grey out.
Did you notice a growing spurt when you first changed your lighting? If so you may need to feed them more and do more trimming.
I struggled to get anacharis rooted in my tanks, it always seem to melt away.
Till I began letting it float a few weeks until it started growing white water roots.
Then I add plant weights and anchor it in place. Mine grow straight up like kelp the look I was going for till I trim them, but...
Their pretty peaceful, the cpd's and least rasbora tend to occupy the lower levels
among the plants and threadfins and harlequins school the middle level.
They are in a 4 foot long 65 gal. heavily planted so there is room and hiding places for everyone