Old tenancy, protected deposit is higher than the 5 weeks allowed

Tenancy Deposits

Hello,

I have an old tenancy from 2016. I realised the other day whilst on the 'MyDeposits' portal (insured scheme) that the deposit amount protected for the tenancy is £600, where the rent is only £450pcm (it's a licensed HMO room).

The £600 deposit is higher than the 5 weeks amount allowed.

Should I:
1) Write and explain to the tenant that I will return their full deposit, unprotect it formally, then ask them to send me a new deposit amount (£500) and protect that amount / issue new cert, or
2) Write to the tenant, unprotect the £600 deposit, refund them £100 and then protect a new £500 amount & issue appropriate certificate doc or
3) 3rd option you might suggest?

Thanks
Tom