I'd like to correct you here, just so you're better informed. Being informed allows you to more effectively research when you do have issues.
Deficiencies that start at the bottom of the plant are caused by a deficiency in a mobile nutrient. That means that when the plant can't uptake anymore, it reallocates the stored nutrients in the oldest leaves to where it is needed most... the new growth.
Deficiencies that appear primarily at the top of the plant or anywhere random are immobile nutrient deficiencies. Immobile nutrients can not be moved around, so the deficiency shows at or very near where the actual problem is occurring.
Now, there are five mobile nutrients: Nitrogen (N), Magnesium (Mg), Potassium (K), Phosphorus (P) and Zinc (Zc). The other 11 essential nutrients, are all immobile.
So five deficiencies which may begin at the bottom of the plant and work upwards, and the rest (11) typically either start at new growth, or at random spots on the plant. It's important too to note that some nutrients, although classified as immobile, can travel some within the plant. Not only that, but some mobile deficiencies don't reliably start at the bottom of the plant always either.
Realistically, from my experience, Nitrogen is the only deficiency that reliably and repeatedly starts at the bottom. All of the others can and do show up in varying locations, immobile or not.