Hi all, my pencil cactus is loosing only it’s lower branches while the rest of it has been growing upwards, outwards, and is green and vibrant. The lower branches keep falling off though, and they don’t ever seem to grow new sprouts from these areas - even during the spring and summer.

Im wondering if it’s not getting enough light? Or if there is something going on with the soil. It’s been about a year since I repotted. I’m very careful to flush the soil out when I water.

any advice would be great.

(FYI - Its plant watering day which is why they are in the shower - usually the plants get mostly full light from a large bay window. the lower half of the windows do have a frost filter - which could answer my question about the lower half not receiving enough light)