It's not going to do you any harm! However because a lot of those herbal supplements contain phyto-oestrogens, being weak oestrogens they can bind to oestrogen receptors but don't allow the full functioning of them so you wouldn't get the full benefit as you would with oestrogen - so they can hinder the effectiveness of oestrogen - well that's my understanding anyway (bit hazy over this!). Best not to take them both together - either do the HRT or the herbal stuff. Why are you coming off HRT?
Hurdity x