Crab apple tree.

I have a 7 year old John Downey crab apple tree that is looking decidedly fed up this year it has blossom but the leaves which are usually large/deep green and very healthy looking do not look so good it has in previous years produced abundant apples, I have pruned it back a bit to keep it in shape not a lot.I have never fed it does any one out there think I should, and what with and when? It is on its own in a very tiny front garden and was planted as a focal point and until this year has done remarkably well I have jars of crab apple jelly to prove it any suggestions would be appreciated,

 

'Well rotted 'oss muck' spread around the base but not piled up against the trunk.

Pruning, 1 remove dead or sickly branches, 2 remove branches rubbing against others, 3 remove old branches from the centre to allow the wind and air through.

Cheers, Tony.