We really need to know all of your numbers if we are to help you understand what may be causing your fish problem.

The important numbers are:
Ammonia
Nitrites
Nitrates
pH
Water Temperature
Types of Fish and number (pounds)
What you are feeding them, how much and how often
Size of Fish Tank Gallons
Size of Bio-Filter/Grow Beds Gallons
Grow Bed area (square feet)
Number and types of plants

With this information, it will give us a much clearer picture of your set-up and help us to help you.

Oliver