I suspect that because the loach are a similar colour and pattern and young Ditichodus tend to shoal, your fish may be trying to establish itself as the boss of the group! Also, they can often become aggressive fish and clown loach are somewhat shy and nervous, so may be bullied, especially when the disti grows and reaches maturity.
Another thing that may be of concern, you have two species there that come from different parts of the world (and different water parameters)and would not normally encounter each other, which I often think may be a behavioural factor in aquaria.