Premna discoloration and bark problem

Hi guys! I'm just a newbie here. As a starter, i purchased a 6y.o. premna (according to the owner). At first it goes well but after a week I noticed that the leaves are turning yellow and the bark begins to crack open which is very soft when tried to pry. Also, I found some part of the branches, that when scratched turns out to be white scales. Now the leaves are beginning to wilt and slowly the bark are disintegrating...

Hope some of the masters could give their advice...Don't want to loose this treasure...Thank you...

Hi
I am not a master, but I think some photos might help identifying the problem. Might be because of over watering or too little watering, or the place you keep it might be too much sun, or such.. Hope it didn't die yet