They say every picture tells a story....it's true with leaves. The leaves of plants are the best indicator of a problem. If the leaves are not healthy, the plant is suffering. Most often the cause of plant leaf issues can be traced back to a deficiency in one or more elements.
That is not to say that all leaf problems are caused by a deficiency, but many are. Sunburn, cold injury, insects, and algae or fungal issues can be the culprit, but if those are not easily ruled out then you need to look at the plan'ts nutrient issues.
Some nutrient deficiency problems are the result of a condition. For example, an incorrect soil pH for a particular plant may be a result of water issues or even chemical use. Incorrect soil pH can prevent a plant from taking up nutrients and will present itself in a deficiency, or in some cases, an abundance of others.
And don't forget your water. Have you had your water tested to see what kind of nutrients are active in that or what the pH is? Every time you water by hand it could have an effect on your plant.
This handy chart will give you a 'general' look at deficiencies caused by a lack of appropriate nutrients. This can vary by plant but keep in mind, there are non-nutrient related problems that could mimic these. Trust but verify!
If you plant appears to have one of these deficiencies - before treating, investigate what might be the cause. Correct the cause and you can correct the nutrient.
