Higenes doesn't matter. It's humidity and temperature. If it is cooler and wet in Africa, the bush is becoming green and also the Phyllocrania.
You should not build up an opinion if you are keeping three ghost, but 500!
The only way you can kill Phyllocrania is keeping them too cool and too humid. Best is 28°C and 40% humidity!
Spray once every 5-7 days, and none will die, but none will become green.
If you just have three ghosts, you should not experiment with them. But if you have 500 it is no problem to keep about 100 very cool and humid. In these enlosures a lot will die, but the approx. 50% of the surviving ones are green.
regards,
tier