For good fertilization it is necessary to respect dosages and administration times. Just try it:)

For example you can use this product (I had good results with these):

dennerle fertilization protocol

• S7 (every week)
  http://dennerle.com/en/products/aquaristic/plant-care/basic-fertilization/s7-vitamix
• E15 (every 2 week)
  http://dennerle.com/en/products/aquaristic/plant-care/basic-fertilization/e15-feractiv
• V30 (every 4 week)
  http://dennerle.com/en/products/aquaristic/plant-care/basic-fertilization/v30-complete

remember that you should create a tank with a lot of plants. The more plants you put the less are the problems :)