In March

In September:

The tree on the left is Cortland and on the right is Red Delicious (almost 6.5 feet tall). Is there any way you can help the stunted tree to grow? What do you think?

There is a very good chance the Cortland will do better next year if it survives. There won't be anything you can do this year to promote growth. Just keep it alive.

Scratch up the soil surface of the Cortland. It looks like it may have a soil mold or fungus that seals out any air movement.

The red delicious appears to have a rootstock water sprout that should be removed. Otherwise the RD looks really nice.

Sometimes a scion variety can't be grafted to some rootstocks. This goes for any fruit type

You could try grafting the Courtland to the rootstock watersprout and have a combo tree.

Steve

Steve, thank you very much, I kept the rootstock sucker just for that purpose, it is so green and bendable right now, almost 3 feet tall and has little roots under soil. When should I remove it? I want to separate them, have separate trees.

Probable safe to remove with roots. If there are only a few roots you will need to cut it back or root it in a vase of water in a bright sun free area and plant when it has more roots.

These roots will not support these twigs in dirt adequately,

Steve