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You want good water flow around and through the plant leaves. So on some plants the lower leaves should be trimmed. You can usually tell because lower leaves will look weaker or have some holes or algae on them. In fact all leaves that have holes are melting or have algae growing on them should be trimmed regularly.
Stem plants can be topped and the leaves on the bottom of the cut stem should be trimmed up some and the stem can be replanted in the substrate. Some times its good to purge the older growth and replace it with fresh stems. Cut the plant just above a node. I usually look for the auxiliary bud on a node to choose where to cut. How low you trim your plant is a judgement call. You want to keep some healthy leaves left ont he rooted portion of the trim so trim low enough for a good stem to replant but leave enough plant mass to encourage the existing stem to continue ot grow.
Sometimes you will just pull a stem plant take a cutting or not and toss the rest because you just got to much of a goods thing going on
Ah... I see them better on my computer than I do on my phone.
Thats usually a good sign that your plants are healthy. However, you can trim those down if you like. Those aren't stem plants, but rather 'rosette' type plants. I would just cut (not pinch) them as close to the base (aka the rosette) as I could get.