Both very much relate to hair heath and strength - for bioavailable vitamin D and a little iron eat more very oily fish like mackerel, herring and sardines/ pilchards, for loads of haem iron eat more organ meats like liver. Even if you are not keen on either both can be made into tasty dishes and you only need fairly small servings.
I am fussy and have trained myself to enjoy both - fish either whole oven baked or in a pate with low fat soft cheese. Liver again as homemade pate, fried with bacon and served with an avocado salad or disguised in a pasta bolognese. To best absorb iron you need to eat with vitamin C rich produce.
Aubrey Organics is richer in oils or butters than the 'true' conditioning agents/ major emollients (fatty alcohols and cationic surfactants), Nourish Spa and Knot Today are richer in plant extracts than major emollients. Oils and butters are not moisturising (add or increase water). The Giovanni and Nourish Spa do contain soy protein tho, it's interesting you don't use them anymore.
It would be worth trying a lighter simpler conditioner - i.e one rich in the major emollients - perhaps containing some hydrolysed protein. I wouldn't use intensive protein on the root area, that should be the healthiest hair on your head so is at higher risk of getting overproteined.
Also overnight coconut oil soaks on dry hair to reduce porosity and increase elasticity. It may be however hair that has grown in weak is beyond saving unfortunately. I know hair that is fried (usually from persulphate bleach) can go mushy, not just hair that is overconditioned. You might consider a hair analysis?
Mineral Oil Versus Coconut Oil: Which is better?
Pedaheh's Hair Blog: GoosefootPrints Hair Analysis with My Analysis Results