Good Afternoon Sue, 

Thank you for contacting the U of M Extension Service. 

Please click on the following link from the U of M Extension Yard and Garden website: 

https://extension.umn.edu/trees-and-shrubs/red-maple

This information states: 

Common problems

At soil pH above 6.5, manganese deficiencies occur that cause chlorotic (yellowish) leaves, stunted growth, and may kill the tree. 

Have you done a soil test? 

You did not indicate where it is located of it was watered often in it's first year and a half. The drought from the past few years has been hard on trees. Since it was a young tree, it would require extra care. Please click on the following link about planting and caring for newly planted trees: https://extension.umn.edu/how/planting-and-transplanting-trees-and-shrubs

This information states: 

• Proper watering, mulching, fertilizing, pruning, staking and winter care will help keep your new and transplanted trees healthy.

Here is a link to a potential issue with your maple: https://mortonarb.org/plant-and-protect/tree-plant-care/plant-care-resources/chlorosis/

Good Luck!