Pereskiopsis

Hello, last summer I was given a pereskiopsis cutting from a friend, which I grew over the summer. Ran into no problems whatsoever and it looks really healthy. Now that it has gotten colder, I had to bring my cactus inside, and buy a growlight for this pereskiopsis. My problem is controllng humidity and how. I can't let my other cactus get too much humidity and i can't let the pereskiopsis get too little. Controlling humidity for the pereskiopsis has been a pain because if it's too much, the top pereskiopsis leaves turn black and rot. This scares me, I want to make sure I have multiple pereskiopsis cuttings to depot next summer. Struggle is getting it to survive that long. Please leave tips and suggestions only if your experienced with pereskiopsis, its not a normal cactus.