New leaves keep flopping over
I bought a hippeastrum last year. After flowering I let the leaves wilt to which I cut them back and placed the pot with bulb in the basement for six weeks. A few weeks ago I brought it up and watered it. It grew very fast and I have four foot long leaves on it. The leaves keep flopping to the side. They'll perk up for a few hours but eventually fall back down.
What am I doing wrong? Does it need fertilizer? More sun, less sun? More water?
The leaves are a new green colour (not dark) and again these are brand new leaves.