Secondly, I had the same difficulty, the clear focusing point is not on the horse but somewhere behind them, except #5. Look at #3, the clear point is right at the trees on top of horse tail.
On nice thing I learnt from your photo is not to change zoom too much. I would guess you used a 18-200mm zoom amd I could tell where your zoom ended. Could you please kindly tell me where did you start with? For example, I did almost full turn from from 70mm and did a full turn. May be a half turn is good enough.