The spa at The Pierre was not open when I went, so cannot comment. Never been to Taj Boston.
Red Flower is not acceptable to me (not as many chemicals, but still too many).
Best chemical-free worldwide are as follows, in no particular order:-
SODASHI -
www.sodashi.com - based in Perth, Australia. They have their own factory which makes the products to order.
The Organic Pharmacy -
www.theorganicpharmacy.com - based in UK. Good spa range. Also produce shampoo, conditioner etc. Also have a very good makeup range.
Dr Hauschka - founded in 1967 in Germany yet still a great chemical-free brand. Available world-wide.
ILA-SPA -
www.ila-spa.com - based in Oxfordshire, UK. Emphasis is on the energetic effect of their products.
KuuSh -
www.kuush.com.au - based in Australia. They have their own manufacturing which hand-makes all products. They do not use any water in the products. Halal certified.
Living Nature -
www.livingnature.com - based in New Zealand. Not geared to spa treatments - mainly a retail brand. Best aspect of this company is its Makeup range.
Suki Pure -
www.sukipureskincare.co.uk - based in USA, but also sold in UK and Europe. The most pure you will find in the States.
There are a few others, like Just Pure from Munich, Germany, which is not at all bad. Not too many, though!