correction: I used few tablespoons of concentrate.

What type of fungicide? What do the directions say? I use Safer brand which is sulfur and it will leave a (light)residue, but I mix according to the directions which I think is 1 or 2 tablespoons per gallon of water(don't have the bottle in front of me).
If you used the proper dilution I wouldn't worry about the residue. If you think you overdid it you can keep an eye on the plants for damage, or rinse it off and reapply if needed.