Hello,
Sorry, there is no such thing as a clear picture of deficiencies. The reason for this is that if there are 400 types of plants then there are likely to be 400 different variations for the same deficiency.
There are some generic symptoms of nutrient deficiency which we can depend on, regardless of plant species. Typically these are the deficiencies of the top 4 required element - Carbon, Nitrogen, Phosphorous, Potassium.
C and NPK deficiencies account for the overwhelming majority of plant health failures. The reasons for this is that these 4 elements make up the bulk of the mass of the plant. For example 40% of the dry weight of any plant is Carbon, so a Carbon uptake failure is, by far the most egregious error we can make. Carbon is so important that a deficiency in this element results is widespread, far ranging and immediate damage. Carbon deficiencies are characterized by structural anomalies in the plants architecture. Any symptom of structural failure can be attributed to Carbon deficiency. This includes melting, leaves falling off, holes in leaves, rotting, browning, deformed leaves or stems, translucency, black spots, brown spots, curled tips and disintegration. Carbon failure also results in certain types of algae such as Hair, Thread or any filamentous algae, BBA (or any version of Red algae), Staghorn and Cladophora. Poor CO2 also contributes to GDA and GSA.
Nitrogen failures are typically characterized by yellowing of mature leaves and poor growth. Shortages of the ion NO3 often triggers BGA (cyanobacterial) attacks and contributes to Rhizoclonum as well as Cladophora.
Phosphorous shortages can result in stunting, but the term "stunting" is relative and may not be obvious unless the hobbyist has seen what a high Phosphorous loading can accomplish, which is accelerated growth and higher levels of colouration. Shortages of the ion PO4 can contribute to GSA, Rhizoclonum and Cladophora.
Potassium shortages are very difficult to pin down because it is so far ranging. There are no algal attacks associated with low K. Poor growth performance is the general symptom because K is used in the mechanism of growth. The growing points of a plant have the highest concentration of K. The high concentration of potassium in the cytoplasm and chloroplasts are responsible for maintaining the pH of the cell and tissue between 7 and 8. In potassium deficient plants, if the pH drops below 7 many plant processes will stop, because the enzymes that perform the many functions have a certain range of activity based on the local pH in the cell, i.e, their activity is turned on or off based on the pH.
The micronutrients are much less important and as with K, there are no know algal forms which are directly attributed to shortages of these elements. Of all the micronutrients, Fe is the most abundant and so it is considered a proxy for the other trace elements. Micronutrient shortages are typically characterized by anomalies in the appearance of young leaves only, such as discolouration or otherwise yellowing, veining and so forth. Again, it's hardly worth trying to determine specific shortages of specific trace elements because of the diversity of symptoms, so when new leaves appear strange but mature leaves appear normal the best thing to do is to simply dose more of the entire trace element mix.
Similarly, if any of the N, P, or K appear to be deficient, it's much simpler to add more of everything. The reason is that if you have a shortage of one, then you most likely have a shortage of others, so the symptoms become a confusing cacophony of syndromes making it very difficult to untangle. So just dose more of everything and that saves you from having to get a Masters Degree in Botany, racking your brain trying to figure out which elements are the culprit. This greatly simplifies troubleshooting. As I stated before, NO test kit can tell you anything about a nutrient deficiency. They are notorious for leading hobbyists down the "Primrose Path That Dalliance Treads." So use these simple guidelines and this will resolve 99% of any problems.
For more specific information on acute or chronic deficiency failures, have a look at
JamesC's Algae Guide.
Cheers,