Spoiled FSG smells sour.
Possibly you didn't clean your bottles well enough between batches. Wash with the hottest water possible. Then swish around some vinegar or rubbing alcohol and let dry.
I use potassium sorbate with vitamin E oil and citric acid. I've been told these work best in combination.
FSG (even with preservatives) will last longer in the fridge.
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2a (nc.com) 2bFi (Fia), very fine, thin, low/normal elasticity, porous, CG, doesn't get weighed down
Cowash: Tresemme naturals
Rinse out/leave in: Renpure Organics (red)
Curl enhancer: FSG
Gel: BRHG, Salon care aloe, Ecostyler Krystal (normal dews)
PT: ION effective care, IAgirl's gelatin PT
Low Poo: renpure (red), Ion swimmers