HelloOur tree has started to in the last week to get a lot of pink leaves

Because it's only been in for a year, it's likely a result of the very dry weather during late March and the whole of April, but you need to cut it back anyway, otherwise it will be over fifty feet tall in short order, so I'd cut off that stressed growth and reshape it to try to keep it smaller and do it every year. Unless, that is, you want a fifty foot tree where you've planted it🤔🙂

I agree its likely down to stress of lack of water early in the year followed by lots of wet in May.

as for keeping it in check I also agree with Bamboo. Most people grow it for the rounded juvenile leaf and that is only achieved through pruning.