Although I've gotten pretty good identifying REAL Kava, @mangrove
, and have quite the Piper collection... I'm not so great at growing Kava.
It's a picky plant. It's an obligate tropical. And it is challenging to grow even in Oceana where it is endemic to.
Browning of the leaf tips and edges is normal for me. All older growth always has at least brown tips. And frequently the margins. But usually only a thin browning along the margin. Starting at the tip but not extending as far as the stem. Short of that I wouldn't worry about it.
On the bottom most leaves, it is not unusual for this 'browning' to turn degenerative, requiring removal of the leaf.
New growth is usually healthy and bright green for some time for me. And stays ahead of whatever browning I have.
I have them in the shade. Humidity averages 70%+ most of the year. It can dip to 40% on rare occasions but only for a day or so at a time. Temps rarely above 95F during the summer. And I bring them into the greenhouse when temps dip into the 50s.
If your browning is more severe than what I described, there may be something else going on. Have any pics?