Dying Orchid

[Nana Trish]

I just bought a Phal orchid 5 days ago specifically because it had 3 spikes and the yellow flowers were so pretty. (I do not repot while blooming.) Three days after buying it, the flowers all fell off. The next day, the spikes started turning yellow. So, this morning, I repotted it, took off the yellow leaves and cut off the dead roots, sprayed the roots with Listerine to kill any bacteria (let them dry briefly), soaked the roots for a couple of minutes in probiotic solution for orchids, then repotted it into a premium orchid mix and did not water it at all. Obviously, on repotting, the old mix was drenched, thus the dying roots, a couple of yellow leaves low, and now yellowing spikes. I have not yet cut back the spikes because I am not sure where to cut them until they stop yellowing. Anything else you would recommend to try to save this beautiful Phal? Thanks in advance for any suggestions!