Chlorosis?

Do you have an alkaline water?

Can be nutrient deficiency or Ph off the charts. Usually Ph is low - acid - when the plant is not repotted for more than a year. Ph high - usually if you have well water with high Ph.

As a starter - get a gallon of distilled water, add just a bit of fish emulsion fertilizer - half teaspoon or less - let it sit in a room for 24 hours to make sure that the water is of room temperature or just a bit warmer - and leach your pots. Slowly pour water from he top - until the water running out from the bottom will become transparent.

Afterwards - consider the above mentioned issues.

Irina