I raise/breed silkies who are prone to vitamin deficiencies, so I have always supplemented their feed with rooster booster granules, but not even 1/4 of the dose. I just wanted the basic panel of vitamins/minerals raised slightly for them. That's year-round. They rarely get mealworms, sometimes some scrambled eggs, and their every-other-day scratch is a layer feed (Henhouse Reserve).
After nearly a decade of doing this and having little to no issues, I'm choosing to slack off to do every other 50# bag of feed or to 1/8 of the dose. The more I learn about which vitamins/minerals aren't naturally excreted if too much and sit in their kidneys or liver, the more leery I get of giving them anything extra consistently. Vit A is one example.