I have grown this apple tree from a seed and so far it has been healthy and growing really quickly.
It sits on my window sill with plenty of light and although it is far down in the plant pot, this hasn't been a problem for it so far.
I water it every day, but never too much as there is no drainage. The soil is damp to touch at the moment. I also give it a small amount of plant food once a week.

I did add some new soil on the top at the same time that the red spots appeared.

Hopefully someone will be able to help before I loose it completely!