Cymbidium with black leaves

[Itsamirmasoud]

Hi all.
about 6 month ago I purchased a cymbidium and when it arrived it was not in good shape. the tip of the leaves kept getting black like it was burnt and I kept cutting the tips.
another problem was the poor condition of the pot medium which forced me to do a repot and it turned out that all of the roots were rotten.

I repotted the plant in semi-hydro to encourage root growth since i had good luck using this method with a phal. but the plant's condition keeps getting worse. after a while the mealy bugs appeared which I tried to contain them with a solution of alcohol-water-soup and now the base of the leaves are turning black.

I attached two photos of the plant in order to give you a better idea of the situation

is there anyone who know what is wrong with this plant or what am I doing wrong ?