Phalaenopsis Leaf tip/edge turn black

[kenngks]

Hi,

One of my Phalaenopsis leaf's edge turned black and started spreading, so I decided to cut the infected portion off early this month to stop the problem.

I just noticed that the tip of the same leaf started to turn black again, as shown in the attached photos. Could someone please advise what I should do to permanentely solve this problem?

It doesn't look like a fungus infection as it is not waterly when I touched it. I followed the weekly weakly rule to fertilise my plants and I did flash them using water only every month end. So it shouldn't have caused by excessive salt built up right?

What should I do now? Can't keep cutting back the inefected leaf.....

Regards
Ken.....