proper way to mix bloom nutes in a garden hose feeder w/o over feeding

hey guys this may sound dumb but can someone fill me in on this......when feeding plants nutes indoors im trying to figure out how do you mix your bloom nutes with the water hose without over feeding .i mean ive heard of the garden hose filters that eliminate chlorine ..but im trying to see how do i mix my bloom nutes with the water from the hose and and get the job done???hope im making sense....but im puzzled....maybe im over or under thinking this?? i bought this thing called the pennington feeder it uses water soluble 10-30-20 tablets but i fed my plants and 2 days later they showed signs of nute burn fast....does anyone have a better way to feed alot of small plants with the feeder?

nobody has ever ran across this problem???