With all due respect...
If you're taking our lack of responses as "not caring"... it's likely because most of your posts regarding this situation come across as very negative and non-receptive to any help we even could give. If I recall... you had started a thread not too long ago about these same plants, and when responses and advice were given, if anything, you shut them down, while continuing to shut yourself down.
It's difficult to really suggest anything or help someone who's coming across like they have no interest in continuing to try themselves, and are beating themselves up so hard over it. I for one, would offer suggestions, but I personally haven't grown dragonfruits before, so I can't offer any useful insight. HOWEVER, in my honest opinion... The photos you had posted before of the same plants, looked like they had small blemishes, likely from weather or the environment, and weren't anything major to be concerned about at the time. I believe others had said similar things, Baja being one of them, and Baja knows WAY more about cactus and succulent care than I do.
I personally believe it's always worth continuing to try, and if all else fails, take it as a lesson to learn from. I also wouldn't have been applying so many treatments to these plants without figuring out what exactly the issue was, or if there IS an issue. Applying so many chemicals is going to stress your poor plants further.
Over all... if this is angering you and making you beat yourself up as much as it appears from your choice of language in your posts... maybe gardening isn't quite the hobby for you? OR, if I'm wrong... one suggestion I could make is, didn't you mention in the last thread that you had a neighbor successfully growing dragonfruits? Why not talk to them and get their thoughts? It sounded like you have someone nearby who's having success with the same plants in your climate, so they could maybe offer some tips or tricks. Most gardeners are quite happy to pass on their knowledge.