question about my fertilizer

[MexicanKid]

Hi i just bought a real cheap fertilizer but its not liquid form it looks like some little colored rocks that you put in the soil and then water. The guy that sold them to me told me they had nitrogen,potassium and phosphorus
can i supplement whit this kind of nutes? or do i have to get liquid form? i also have a foliar fertilizer can i use this too on my 2 week plants?

Thanks