Adding fresh water first is a good idea, it soaks in and spreads out so when you do feed it doesn't burn. kudos!
I always added fresh water till I got a good run off, so I could see ph diff. then add your feed.
I wouldn't go a teaspoon per gallon yet, go at half strength and see how they respond. 5 gal...use 2 1/2 - 3 teaspoons of nute.
but usually when they say on the amounts to mix, its says, 1 tsp per gallon of water and your doing 5 gallons. well you know the math.
always go a little under, cause you cant take back and over fert plant. but you can add...