It could be simple seasonal allergies or it could be an eye infection or even an upper respiratory infection, which will also cause watery eyes.. The best things you can do at home right now is to irrigate the eyes and make sure they are clear of any debris or pollutants. For the diarrhea you need to start with the sympathetic method of withholding food for 12-24 hours then start back with a bland diet of cooked chicken and rice which will help aid in the diarrhea. I have also supplied some information below concerning the eyes, diarrhea, and upper respiratory infections. I hope they will be of help to you.
For the diarrhea:
Acute diarrhea is a common clinical problem in veterinary practice. It is characterized by a sudden onset and short duration (three weeks or less) of watery or watery-mucoid diarrhea. Occasionally the fecal material is also overtly bloody. Diarrhea results from excessive water content in the feces and is an important sign of intestinal diseases in the cat. Diarrhea can affect your cat by causing extreme fluid loss, which leads to dehydration, electrolyte disturbances, and/or acid-base imbalances.General Causes
For a possible upper respiratory infection also watery eyes:
Feline upper respiratory infection refers to infections in the area of the nose, throat and sinus area, much like the common cold in humans. In cats, these infections are quite common and very contagious. The two primary viruses involved are feline herpesvirus-1 and feline calicivirus. Feline chlamydia, a bacterial infection, can also result in upper respiratory tract infections. Cats that recover from feline upper respiratory infection will periodically shed the virus throughout their lives in times of stress. It is uncommon for the cat to have a reoccurrence of the upper respiratory infection but they are considered a reservoir for the virus. These viruses do not live long in the environment and are easily killed by household cleaners, such as bleach. Unfortunately, unsuspecting owners can carry the virus from an ill or viral-shedding cat to their homes. This is a common way that feline upper respiratory infections are transmitted.What To Watch For