Help with Plumeria leaves turning brown/fouling
Just recently purchased my second plumeria obtusa online, the first one didn't survive the winter (maybe too cold, or watered too often, dunno). anyway, received this plant about three weeks ago, put in a nice sunny place (corner between two windows), and waited for the leaves to start growing. the first three came out just fine, but now all the new small leaves turn first brown then black, and the tips of the branches where the new leaves grow out of also appear black.
Any ideas what could be wrong (watering too often, not often enough -- how often should it be watered anyway, instructions said not very often which is kinda vague)?
any hints are greatly welcome, would really like to get this plant to flourish, always loved them when on vacation somewhere nice and warm ;)
btw: plant location is in austria, indoors, in corner of east and south facing windows, temperature inside 22-25 C, humidity between 35-45.