citrus tree

Question

Grapefruit have been really small last 2 yrs. This tree has always produced great fruit. 

Answer 1

The fruit may not be getting enough phosphorus and potassium in the mix. Alternatively, they could be getting too much nitrogen. Here is a link that will help for all general citrus: https://www.gardeningknowhow.com/edible/fruits/citrus/citrus-fruit-thick-rind.htm