One is yellow water, that is, pouring too much water leads to long-term accumulation of soil moisture, poor air permeability, and even some fibrous roots rot. It shows that the tender leaves are dark yellow and dull, and the new buds shrink.
The second is fat yellow, that is, fat, which shows that the tips of old leaves turn yellow and fall off, and the new leaves are plump and shiny but generally concave and convex. If it is a precious flower, you can sprinkle a layer of Chinese cabbage or radish seeds and pull them out a few days after emergence to consume nutrients.
The third is drought and yellow. Due to long-term non-watering or dehydration, although the color of new leaves is normal, the lower leaves gradually turn yellow, fall off and age.
The fourth kind is alkaline yellow, especially some flowers in the south like acidic soil, while the leaves in the north will fade, turn yellow or even fall off when the water quality is alkaline. The simplest way is to pour fermented rice washing water or rainwater.