Gardening and Horticulture - Fish for small pond

I installed a small pond 2 weeks ago, about 5ft x 4 ft x 1 1/2 deep. Purchased 2 channel cats and 3 Shubunkins. Also have a fountain, small waterfalls, 3 large plants and about 12 water hyacinth. Feeding fish Vitakraft Pond Menu. 2 of the Shubunkins have died within the first week, one after 3 days and one after 7. Channel cats ar doing fine so far. None of the fish stay visible, usually hide in plants.

Questions 1.Why have the 2 fish died so quickly?
2.Should I switch to Goldfish or Koi? (pond seems too small for Koi)
3.Am I using the right food?

As a "new guy" a this, I would appreciate any input.

I would like to pass on a couple of things that, after doing a fine pond a few years ago, I learned.The #1 cause of problems,aside from disease,in a new pond are the buildup of ammonia.This is caused from the breakdown of organic matter from uneaten food,fish urine and waste and anything else that tends to break down.If you don't have an ammonia test kit you must get one.Anything over 4to5 parts per million can equal 50% death rates.This ammonia buildup will be counteracted in a mature pond by anaerobic bacteria.A layer of gravel in the bottom of the pond will provide a home for these needed bacteria.Constant aeration and regular 20% water changes will cover you until you have a biological system in place.One other thing to consider is the PH of the water.Most fish require a PH of 7.0 or higher and most water supplies,at least were I have lived,are below that.If you can get a book that deals with the biological system in depth you will be able to get this very important system in place.I know I havn't dealt with your questions as asked but have tried to pass on some info that took me a year(and many fish)to learn.