Generally speaking a physiological disorder is a problem caused by something other than a pest or a disease. For instance, it might be that the plant is not getting enough nutrients or it might be getting too much water.
You will find that the weather always has a role to play and, despite your best efforts, too much or too little water or warmth can ruin the best laid plans. Don't despair! Most plants have a tremendous capacity to recover from adversity and even if they don't there is always next year.
Although we can't control the nutrients or weather in your garden we can help to inform you of what can go wrong and what to do to remedy the situation.