Not sure about Geneva, but fish oil you can get in a pharmacy Gaillard very cheap. All medicines, including natural ones, are 2-3 times more expensive in Geneva than in nearby France.

Curcumin as a spice you can get in any bigger shop like Geant in Annemasse.

What you mentioned can be bought in Migros! 

The Pharmacie du Grand-Pré, they also have their own brand of products that are much cheaper than elsewhere. And very competent advisors Droguiste-Herboriste, specialists of natural products.

http://www.pharmacieplus-grandpre.ch/

In the Droguiste et Herboriste d'Arve, you will find an elderly gentleman, probably the oldest and most experienced Droguist-Herborist of Geneva, with a very wide variety of natural products.

87, rue de Carouge, tram 12 stop Blanche

You can also check the organic shop called “La Marché de Vie”, which is at 25 rue des Eaux-Vives, 1207, just across the road from the Pharmacie des Eaux-Vives. Their prices for some products, Epsom salt, for example, are comparable to those of Satoriz in France.

Some local pharmacies are getting into the natural movement too, a good example being Pharmacie des Banques at Rue du Stand 62, 1204, who advertise themselves as “Your pharmacy specialised in natural medicine”:

https://www.pharmaciedesbanques.ch/en/

As others have mentioned, if you are looking for supplements, such as Gingko Biloba, Curcuma (Turmeric), Harpagophytum, etc. the Satoriz chain in nearby France has them all neatly ready often for a better price than in Switzerland. However, if you would like to make your specific blend of different ingredients, I would give Pharmacie des Banques a try. Their English is very basic, so if you need a complex mix, it will need to be communicated to them in French. 

Good luck and keep well!