Phalenopsis black on base and yellowish indent on leaves

[OdessaOrchid]

Hi I'm just getting started with orchids but unfortunately now I have a sick Phal. I got it about 2 months ago and it had 3 spikes and two plants. One of the spikes bloomed and then almost immediately dropped all of its blooms. I thougth it was due to a lack of water but since have noticed that the leaves are falling off while they are still green with some black at the base. Today I took both plants out of the pot cut away the dead roots and put peroxide where the black is on the base. On the other plant in the pot, I am now noticing a yellowish indentation in the leaves on the top and underside and something that looks like it might be scale. Can anyone help me identify the problem and tell me if I can save them or if I should destroy them so they don't spread the stuff to my other orchids?