Cymbidium issue

[The Orchidist]

This is my first cymbidium , i got it in january and it had not been blooming for me, i put it into a larger black pot and using spag moss ,roots seem white solid and large root mass, i am wondering why all my leaf tips keep turning black, i have trimmed the tips off a few times. But within weeks they are black again , there are a few new growths from the base , just not sure if its too wet , too much nutes or if i have feeding schedule off.
Any suggestions would be good







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