Advices Need on Stem Plants

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I have a couple of questions regarding stem plants.

1. Some of my stem plants are not growing upright. It either curve to one direction or arches. Is that normal or is it due to some nutrient deficiency? What can I do to help it grow upright again?
2. After trimming, the portion of the stem just above the node turn an ugly black like it is melting off. Is that normal? Are there best practices to trimming of plants? Will the black portion fall off over time?

TIA

[Jimmy]

Stem plant to cut off bottom part & replant top part, discard the bottom part.

[Urban Aquaria]

If your stem plants are growing in a curved or arched pattern, it could be due to another light source coming in from the side of the tank (ie. window or bright corridor), and the stem plants are growing towards that light source. Some stem plants can literally change their arch direction in a matter of minutes to face new light sources.

If thats the case, then simply draw the curtains or close the doors to reduce those other sources of light, so that the stem plants receive light only from the aquarium light overhead and hence encouraged to grow in a vertical pattern.

As for trimming stem plants, its normal for the leftover stem tip above the last leaf node to turn black and melt away, its the dead part as new stems will only grow and branch out from the top of the leaf node.

What you should do is trim the stems as close to the leaf node as possible, so that there is no excess leftover stem. That will solve the black/melting tips.