Claim against tenant's damage from their deposits

Tenancy Deposits

Can anyone advise me on this situation? On Sept 1st, I found a broken antique glass chandelier at the end of a student tenancy that was removed by an electrician because it had a metal chain and was not deemed safe. But the electrician failed to inform me that he had removed it, otherwise I would have taken action to protect it.

The students didn't tell me that the chandelier had been left on the floor either and they put it in a cupboard with stuff piled on top of it where it subsequently broke beyond repair.

As the students had a duty of care to my possessions and allowed the chandelier to get broken, I am asking for £150 from each of the 4 relevant tenants deposits towards a replacement (this wouldn't cover the whole cost).

One student has agreed to this and has paid and the other three are objecting, blaming it solely on the electrician and taking no responsibility for it themselves.

In the past when I had a claim against a tenant leaving the place in a mess, the DPS believed her, not me. So I worry the same will happen again and I would appreciate your advice on how best I should proceed?
Thanks so much in advance.