well... for start you forgot to include your nitrogen dosing :p. Secondly... you should look into finding a place to buy yourself dry ferts and save yourself hundreds of dollars over the course of a year. Here is why: Seachem products are pretty watered down, and the dosing they recommend is pretty low.
If you are sitting at the level of about 3WPG with CO2 then you will need to dose much more than this- especially if you have fast growing plants.
I use this site to get the desired level of ferts in my tank when using Seachem products: FertFriend
. I have been using daily dosage for the following ppm (the result from the website) to be about 3.5ppm N, 0.25ppm P, 0.7ppm K, .15 Iron, mixed with 5ppm Flourish every other day. I have been getting amazing results with this mixed with 3WPG and CO2 supplementation.
A few hints for this calculator: a) I have no idea how accurate it is. b) Notice that the volume it wants is in litres, not gallons. c) don't use the size of you tank, but about how much water is actually in there. Remember that wood plants and gravel all take up space. For my 20G I guess that I have about 17 gallons of water in there and the rest of the space is taken up. It is a rough estimate, but it is better to be on the small side then to dose too much.