I am not familiar with the design of the aquarium you have but the amount of light required will depend on a number of factors including the type of light, water depth and clarity. Four hours seams way too little---I have lights on 16-17 hours/day (10 - 12 hours would be about normal I would think). Algae needs nutrient and eventually the plants will use a lot of the nutrient and starve the algae. In the mean time you should do larger and more frequent water changes to reduce nutrient. I do 50 to 60% water changes in well established, heavily planted tanks. Cycling is where the waste products from your fish are converted to other compounds by bacteria and eventually removed by plants or water changes. Some of the compounds formed are toxic to fish and may be killing yours. Eventually the bacteria will grow to establish a balancece and all should be sweet. Only feed what the fish can eat in 5 minutes---no more as this creates nutrient. Good luck.