Q.Sago palms
I have a group of three Sagos and one is turning yellow. I had scale on two of them and washed them clean and sprayed them with insecticide. A year and a half ago I did remove three baby plants crowding the one that’s turning yellow (not sure if that I created this problem or if it’s something else). I live in southern Texas.

Certified GKH Gardening Expert
The yellowing sago palm may be suffering from a nutrient deficiency, which could have been caused by competition from the baby plants. Please see these articles for advice:
https://www.gardeningknowhow.com/ornamental/trees/sago-palm/sago-leaves-turning-yellow.htm
https://www.gardeningknowhow.com/ornamental/trees/sago-palm/fertilizing-sago-palms.htm

It could be a nutrient deficiency and/or a soil pH problem. But you should contact your local Texas Cooperative Extension master gardener for advice. Go to this page on GardeningKnowHow to find your local master gardener in Texas: https://www.gardeningknowhow.com/extension-search/ . I also strongly urge you to have a soil test done (possibly sponsored by Texas A&M in your area) for your sago palm so that you can be given the proper advice on how to amend the your soil in order to restore your sago palm to its original beauty. Here are some basic tips on sago palm care: https://www.gardeningknowhow.com/ornamental/trees/sago-palm/how-to-care-for-sago-palms.htm

It could be a nutrient deficiency and/or a soil pH problem. But you should contact your local Texas Cooperative Extension master gardener for advice. Go to this page on GardeningKnowHow to find your local master gardener in Texas: https://www.gardeningknowhow.com/extension-search/ . I also strongly urge you to have a soil test done (possibly sponsored by Texas A&M in your area) for your sago palm so that you can be given the proper advice on how to amend the your soil in order to restore your sago palm to its original beauty. Here are some basic tips on sago palm care: https://www.gardeningknowhow.com/ornamental/trees/sago-palm/how-to-care-for-sago-palms.htm