I have no idea why. I do not add salt and I prepared them as I always do.
There was only oats, yoghurt (natural - homemade, no additive), milk (dairy), fruits (blueberries, grapes, physalis) and seeds (pumpkin and sunflower).
A mystery, Sherlock, but is there a chance of Cross-Contamination:? This is the most likely scenario . Was the spoon or container you used to scoop the yogurt used for something salty earlier?
