There is no statute of limitations on this sort of thing, they are ongoing issues.
In respect of the failure in relation to hot water tank inspection and maintenance, this is serious. If the insurance company required the owners corporation to do those things, if something happens it is likely the insurance company can refuse the claim. I would be writing a very serious letter to the Committee and the management company, so it is on record. One option is to say if you do not take the steps required by the insurance company we will hold you liable.