When your plants' leaves turn yellow, you should try to troubleshoot the problem because there probably is something wrong with your plant. It will be important for you to figure out the root cause of the yellowed leaves for you to be able to resolve the issue. If you don't know what to do when your plant leaves turn yellow, your plant may die. Here are the steps you can take when plant leaves turn yellow.
Yellowed leaves may be caused by too little or too much light, so adjust how much light you are giving the plant to see if that helps to resolve the problem. Some plants prefer not to have too much light while others need more light than you think so make sure to test a few days with less light and a few days with more light and see if the plant gets any better.
If you are providing too many or too little nutrients, your plant will also react poorly. Yellow leaves may be caused by nutrient deficiency or worse, bad health caused by too much fertilizer. Plants are like animals where you can't feed an animal too much otherwise it is bad for their health.
You can test the soil to see if it needs any nutritional boosts with fertilizer or if it has too many nutrients so you can adjust fertilizer usage accordingly. Another important thing to look for in checking the soil is if it is draining properly and if the water is drowning the plant which can be another reason why the leaves turn yellow.
If your roots have begun to mold or rot, then they are unable to absorb water and nutrients from the soil causing deficiency, so while a soil test may tell you need to add some more fertilizer for the plant, that won't work if the roots are spoiled, so if trying most of the above doesn't work, make sure that you check the roots to see if there is a root issue with your plant.