Yes, the "deficiency and excess" pictures on the charts do make them look alike.
The larger the plant the more it needs in the way of water and nutrients to maintain that size. So, I think of a deficiency first. If the plant is entering or already in the flowering stage it demands even more just to maintain where it is already at; so again I think of a deficiency first. Growing in a natural soil makes it hard to believe that the leaves turning yellow or brown is because of an excess if for no other reason than the plant itself and soil organisms are controlling what and how much is available.
If the plant is in a natural soil the first thing the plant does is make use of the water soluble nutrients that are available. When the levels of water soluble nutrients are not enough the plant sends out 'signals' that it is looking for the missing specific nutrients and the amounts. At that point the micro-organisms living in the soil will be eating the "water insoluble" raw materials and processes and then exuding what are now water soluble nutrients. The needs of the plant are taken care of.
The process makes it near impossible to have too much of any of the nutrients become available faster than the plant can handle. The plant cannot take in an excess unless it is already water soluble and it takes the micro-organisms to make the "insoluble" become "soluble" except in rare cases. Feeding with organic input or natural fertilizers makes it harder for any excess to become a problem considering most of it is not available to the plant until the organisms do their part.
This process is not just for Marijuana plants since all plants growing in natural soils go through the steps of interacting with the soil micro-organisms when it comes to the need for nutrients.
Since I am growing in a natural soil mix I tend to look at all grows that way unless the grower says they are not in a natural soil. Those who are growing in a hydroponic or a soil-less grow medium end up having a different process taking place than what I described. Their feeding schedule involves feeding weak doses with the water soluble nutrients already available. Often their fertilizers do not have water insoluble nutrients since what the plant needs has already been dissolved and is ready to go immediately. Even if it is a weak dose, giving the plant a double dose in one feeding can cause signs of an "excess" as we see in the charts.
