You have at least 2 problems going on. Let's address the mites first. Either Hi Yeild, or Meyer's 10% Permethrin Indoor/Outdoor formula will do the job. Same stuff, different brands. There are 2 nearby feed stores near me that each carry one of the brands, so you stand a good chance of your feed store having it, or you can order it on
Amazon. I mix it according to directions in a 2 gallon sprayer, then pour some of that into a spray bottle. First, spray the chickens with the spray bottle, getting it under their feathers some, especially the vent area. Be careful not to get it in their face, or eyes. For that, spray some onto your fingers, and rub it on their comb, wattles, and head area. You don't have to soak them down.
Next, move the chickens out of the coop, and all their food, and waterers. Remove all bedding/nesting material, and dispose of it. Now, spray the coop, especially all the wood, getting into the nooks, and crannies where the mites hide. Spray the roosting area good, and the nest boxes.
While that dries a bit, wash all waterers, and feeders inside and out, with soap and water, paying attention to the outside of their waterers, and feeders, in seams, crevices, rims, etc., where mites can hide. Rinse it all well, then put all new bedding in the nest boxes. Fill the waterers with fresh water, and the feeders. In 7 days you will repeat this on both the chickens, and your coop. After you repeat this, go out later that night with a flashlight, and look at the roosts, nest boxes, etc. to see if there are anymore mites. Northern Fowl mites only come out at night. If you see any, repeat for a 3rd. time in 7 days. If you don't see any, you don't have to repeat the 3rd. time.
Now for the second problem. Little grain of rice looking worms usually means it's going to be tapeworms. That might not be the only worms, just the ones you're seeing. Valbazen is pretty broad spectrum when it comes to worms. Since you are probably dealing with tapeworms, and it's unknown about any others, Withold feed for 24 hours, then dose the chickens by weight. Repeat in 10 days.
Weigh, and record the weight of your chickens. If you have quite a few, and they are similar in size, take a random sampling, and weigh them.
