help! i got this curly cactus plant about a month ago, repotted it in some cactus/succulent mix, and have watered every 2-3 weeks when the soil feels dry. these black dry tips started appearing on some of the leaves, i’ve taken off some of them already too. where am i going wrong!?! the leaves don’t feel squishy or brittle, last watered about a week ago and the soil is still moost