[header] How to identify deficiencies in container plants [title] Check for poorly defined green shoots, yellowing older leaves and premature leaf drop. [step] If these are present, this indicates that the pot plant has magnesium deficiency. Remedy by spraying a mixture of water and some dissolved epsom salts to the soil and on the plant's leaves. 
Try to spray under the leaves for better absorption. [title] Look for spindly growth and dropping leaves that turn red or purple.