I'm sorry to hear about your losses, I know it can really hurt to lose our little friends, but it's part of life.

Even here in my city I hear people say they lose cacti and they have no idea why, I guess it must be because of the mix and the ventilation of the place, the other day I was invited to a garden to look for the reason why many of the cacti were getting sick and dying, and the reason was the lack of ventilation, I recommended him to move his garden to the roof and it seems that everything is going better.