Sarevan is correct. DE, ACV, electrolytes are all ineffective against worms and lice/mite infestations. Pick your rooster up and visually inspect him for lice/mites. Lice or white or off white in color and move fast among feathers. Mites look like pepper or can be red in color, move slow or not at all and have 8 legs. Especially check around the vent area. Worm your rooster with either valbazen liquid cattle/sheep wormer or safeguard liquid goat wormer. Use one wormer or the other. Administer either wormer using a syringe without a needle. Dosage is 1/2cc orally undiluted. Repeat dosing again in 10 days.
DE is hyped and a waste of money. Take it from someone who knows.