Shibui
Imperial Masterpiece
The new photos show black bark on those dying branches. No way to save those now so they should be cut out below the black. The future is in the new living branches. Bonsai is often about changing and replacing existing growth so it is normal for us to prune branches.I took pictures of all the main branches. The first two pictures are the branches from last night’s pictures.
I agree with the soil diagnosis. White salts buildup usually indicates chronic under watering. Soil needs to be thoroughly wet to the point of water running out of the drain holes every time it is watered to flush out unwanted waste. The pot should not permanently sit in a saucer of water except maybe really hot mid summer or short vacation.