It may be that the dismissed have just looked at the law and seen that the only way they will now get their jobs back is if they are given them by the company.
There are stringent time limits for bringing claims in employment tribunals. These vary dependent on the type of claim being brought. For some claims, the time limit is three months. Employment tribunals do have the power to extend these time limits but only exercise this power in exceptional circumstances.
Full details here:
Employment Tribunals