Two of the most common ways people kill cacti is through overwatering and planting them in the wrong potting media. Firstly, please, stop watering them so much - they don’t need it, secondly - give them the mix these spiky heroes deserve! There isn’t a one size fits all for plant soils, what works for a Monstera isn’t usually going to work for a cactus.
Cacti and succulents are traditionally found in arid sandy places (you’ve got a mental image of a desert for a reason) and the cacti’s shallow roots are used to loose, well draining soils. The stuff you find at the local garden warehouse isn’t usually the best, often made with cheap ingredients that clump around the roots and lead to root rot. So - we’ve some time designing the ultimate soil mix for Succulents and Cacti so they can stay alive and thrive.