Pumpkin seeda will NOT eradicate worms in chickens. Give them some, ad then take a fecal sample to your vet. That will convince you.Tractor supply had Diatomacheous Earth (DE) last time I visited - DE which is mostly "ashe" according to the ingredients but is good for lots of pesky tiny insect issues from worms to mites and ticks apparently. I've also sometimes sprinkled a little borax powder around their perimiter area to ward off fleas, ticks and other insects.
The easiest dewormer you can get this time of year is pumpkins (just bust it in half and toss it into their area). The seeds are great dewormers and they love the flesh for food as well. To top it off it is most likely organic, healthy inexpensive chicken food too.
As far as complicated vitamins and minerals - I usually just add some molasses to their feed - just feed them a few shredded carrots, couple of sliced/diced apples/tomatoes and pour a little molasses on it maybe throw in a few scrambled eggs with that and stir it up - they go nuts and look healthier. I've also been known to get simple bird feed (seeds) and toss in a scoop of that.
They also love day old spaghetti/pasta leftovers and canteloupes.