Q.Back To Blanco Oro Frankenstein Fruit.
Notice skin, shape, meat that shows seeds and is tart and dry. Ruby Reds in same yard are amazingly good. I hope you see images, I uploaded 4.

BushDoctor
Certified GKH Gardening Expert
Certified GKH Gardening Expert
Answered on January 18, 2021
I do see one image. This looks to be a lack of Sulfur, and in many cases a lack of Phosphorus and Potassium, too.
Here are some articles that will help:
https://www.gardeningknowhow.com/edible/fruits/citrus/citrus-fruit-thick-rind.htm
https://www.gardeningknowhow.com/edible/fruits/grapefruit/growing-grapefruit.htm
Was this answer useful?
00