Regrettably the left hand picture were my fingers after a few very long bike rides which created an EFA (essential fatty acid) deficiency for me. This is evidenced by the dry, peeling skin on the ends. The good news is that this is very temporary when understood. When my fingers look like this, I take and extra 1-2 fish oil capsules and they skin is better within hours.
The white spots in the right hand picture demonstrate a zinc deficiency. This sometimes magnified by a need for HCl (stomach acid). Zinc is necessary to make stomach acid, it helps the hormone system, and it helps the immune system. Notice the poor circulation and immune problem of the last 2 fingers. Sugar consumption and stress depress zinc levels.
Cracking or brittle nails are often a need for calcium and HCL which will help one metabolize the calcium.
Perpendicular ridges across the nail are periods of protein deficiency. A sign that you need more protein in the diet. Don’t let this continue or you will end up quite ill.
Loss of the half moons at the nails beds are an indicator that there may be some hypothyroid issues. This needs to be correlated with symptoms and appropriate testing.
Anemia is another issue that may show up as spoon shaped nails or possibly as deeper longitudinal lines. Correlate with signs like a lack of redness in the “life lines” of the palm, slow color recovery after squeezing the finger and lab tests.