Help ...
Recently received a Dendrobium Nobile as a gift ... the orchid did have mealy bugs for which I treated with alcohol.
It also had some suspicions black areas on the undersides of the leaves that I treated with hydrogen peroxide .
I also trimmed the dead roots and repotted.

Sadly I'm still struggling with yellowing leaves , suspicious black spots ... and the spots seem to be putting the leaves ...

I'll attach pics ...
Any help would be appreciated

Did you wash off the alcohol and peroxide after you used it? "...and the spots seem to be putting the leaves .." What? Are new leaves yellowing? Or just the old ones that had problems in the first place?

I doubt you got rid of the mealybugs in one try so keep looking. The black spots could be mold and, without good air circulation, will continue. Dendrobium Nobile does lose all the leaves on old canes. It could be still recovering from your re-pot.

You are using too many chemicals way too often.
Dendrobium nobile likes water and then dry out slightly. The pot you have selected is too large. Dendrobiums like to be under potted, tight at the roots. I think that there is an excellent chance that you are causing the problems you are seeing. When you purchase a new plant, it is stressed. From grower to you causes stress, you spray it with chemicals causing more stress. It is over potted or even repotted, more stress!
Just chill for a while, let the plant adapt to your conditions. But when Dendrobiums are stressed those little black spots develop.
Meanwhile, welcome to our Orchid Forums. Go back through some of our threads. I posted one last June or July on how BigBill repots Dendrobiums. This might be helpful.
Read through our other forums too, they are full of good information.