From my perspective, those brown, crispy spots, often in the center of my uppermost leaves, are a clear sign of distress. I call it sunburn. Just like you, I can get too much of a good thing. My succulent leaves are designed to store water and thrive in bright light, but if my exposure to intense, direct sunlight is increased too rapidly, my photosynthetic tissues get damaged. The UV radiation essentially fries my cells, causing them to die and form a permanent, scar-like patch. This is most common when I'm moved abruptly from a sheltered spot, like a nursery shelf, to a full-sun windowsill or outdoor garden without a gradual period of acclimatization.
When the brown spots are softer, darker, and seem to spread from the base of my leaves or the stem outward, it is often a sign of a microbial attack. This is frequently your fault, I'm afraid to say. If my soil is kept consistently wet or there's water left sitting in my rosette, you create a perfect environment for fungi and bacteria to thrive. They attack my tissues, causing rot that manifests as mushy, brown, or black spots. If the infection is caught and the wet conditions are corrected, the affected areas will dry out and scar over. This scarring is a testament to the battle my immune system fought against the invaders.
My leaves are plump and fragile. Even minor bumps, brushes, or pressure can cause internal damage. You might not see it immediately, but soon after, the injured cells will break down and oxidize, turning brown and callousing over. This is simply me healing a wound. This type of scarring can also occur from pests, like mealybugs or scale insects, piercing my epidermis to feed on my sap. Their feeding sites leave small, damaged areas that subsequently scar. While unsightly to you, these scars are my badges of honor, showing I have sealed off the damage and protected my inner systems from further harm.
Sometimes, the problem originates from my roots. If you water me too much or the soil does not drain quickly enough, my roots absorb more water than my leaves can transpire (release). This causes water pressure to build up until it literally ruptures my cells. These ruptures appear as small, rough, corky brown spots, usually on the underside of my lower leaves. This condition is called edema. It is not a disease but a physiological disorder. The spots are the permanent scars from where I burst under the internal pressure. Once formed, they will not go away, but you can prevent new ones by watering me only when my soil is completely dry.
