Amazon Sword stalk broken and detached

[Phyroath]

My amazon sword is growing fast. Yesterday, i noticed the stalk of the newest leave is broken then detached from the plant. I took it out and the leave all look healthy. Neither me nor the fish disturbed it (I have only a pairs of swordtails). Can anyone help what caused this?

[StereoKills]

Hard to say, but it shouldn't effect the plant's growth too much.

[Phyroath]

Thanks Stereo - I removed that nice leave. Have not yet seen any new leave coming and that why I was so worrying.