The friendliest place on the web for anyone with an interest in aquariums or fish keeping!
If you have answers, please help by responding to the unanswered posts.
I don't use EI as I don't like overdosing ferts which is a waste IMO so I can't really help you any further with that.
I just ordered some stuff from Bob's Tropical Fish and he had individual dry ferts for sale. That is a place to start looking. Also I've seen people on The Planted Tank Sale Forum selling them individually.