Apple tree seedling not growing properly
I'm sorry this is my first post, but I'm desperately trying to find out what's wrong with my poor apple tree seedling, and after scouring both the internet and my gardening books without success I couldn't think of anything else to do.
I have been growing this plant for a few months now, and another young tree grown from a seed from the same apple has grown past my knee and has plenty of healthy leaves. However, this one was afflicted by a grey mildew while it was growing its first buds. When I couldn't find an anti-mildew spray suitable for fruit trees, I just washed the mildew away and hoped for the best. While this seems to have gotten rid of the mildew, my apple tree is still stunted and has not grown any real leaves in over a month, even though the stem itself seems quite strong and is definitely still alive.
Is it in some form of shock? Is there anything I can do to help it? I've thought about pruning the top of it to try and promote further growth, but I'm afraid that might just kill it off.
Any help you can offer would be greatly appreciated!