Housing element in Universal Credit

Housing element in Universal Credit
I live in a 2-bedroom property with my disabled wife and adult daughter of age 32. It was a privately rented property with monthly rent £1350. My wife was on PIP Daily Living standard rate, I was on Carer's Allowance, we were on Income Support and daughter was in full employment. We were receiving Housing Benefit as £623 fortnightly ( Housing Benefit was £1350 monthly same as our rent, London Housing Allowance is £264 per week in N17 9SJ area for 2 bedroom), daughter was non-dependent and she was exempt from any deduction from Housing Benefit as my wife was on PIP.
Then in Nov 2018 my wife's PIP was stopped and we (myself and wife) had to apply for Universal Credit. We received £1398 monthly out of which £498 for living and £900 for housing. I asked UC why Housing element was so low. They said rent (£1350)was divided by 3 because we three (wife, daughter and I) were on Tenancy Agreement and we received £900 for myself and my wife. They didn't mention any LHA or non-dependent issue.
Then in February 2019 our daughter moved out. I still live in the same property with my wife. My wife won her PIP appeal in June and is now receiving PIP Daily Living standard. But Universal Credit told me that our UC payment of £1398 remain unchanged and it will increase only if I receive Carer's Allowance. Even then housing element of £900 will not increase.
However, in previous system of Housing Benefit we were receiving £623 fortnightly (£1350 monthly) when my wife was on PIP and now only £900 monthly. Are they (UC) calculating Housing element correctly?

Gordon
I see your point. but this is not about Housing Benefit. This is about Universal Credit which covers housing element. My query is about this. Sooner or later we all are going to be affected by Universal Credit.