Once one has a niacin issue already the liquid B complex @Jenbirdee mentioned is the best for getting them over it. Then rec to use Nutritional yeast after they are not limping for at least a week. . Pekin just seem to need more niacin and also more Calcium since they are usually heavy layers.
What type of niacin do you have because flush free and time released won't work.
What type of niacin do you have because flush free and time released won't work.