Hey Maddie, I suspect your cactus was overwatered, perhaps by Lowes.
I water all my cactus once a month during the winter months. All get
some some sun, then *some* are placed out on the deck (without
saucers) during the summer months when I feed them with some diluted
fish emulsion. I prop the pots up on two sticks for fast drainage.
My pencil cactus survived some sunburn last summer. In Oak Ridge,
TN