I'm curious - are you trying to correct a nutritional imbalance? Complete feeds already have a vitamin/mineral package which is generally sufficient for the age of bird for which they're designed. That being said, I understand that vitamins will sometimes degrade from feeds because of storage, turnover, etc. However, the vitamins that do are often oil based (A, D, E) and those particular vitamins do not do very well in a water based vitamin additive.
You end up over supplementing some vitamins/minerals by giving all vitamins in the water, which puts the others out of balance.
It's really best to let the chickens do the work that they are supposed to do and encourage that. Keeping their beneficial bacterial load at its peak will do most of the work of providing the correct amount of the B vitamin spectrum for chickens. Vitamins A D E are best give as a more natural, not chemically produced, oil based supplement and then not overly frequently because oil vitamins store in fat and can overdose. Birds do not excrete them as they can water vitamins. Even water vitamins are excreted but they can cause strain on the kidneys if the kidneys have to work too hard to constantly extrete overages of water based vitamins.
Minerals are a whole other ballgame. Mineral/vitamin interrelationships are so very delicate.
So I guess the main question is: why? What is it that you'd like to do for your birds at this point that you feel vitamin/minerals will help? Conditioning? Treat them the best you can? Other?
Honestly, I like to only use water based vitamin mineral packets in the case of a shocky bird, one that was horribly malnourished and is on a feeding-up program, or.... well no that's pretty much it.
I do understand (and greatly appreciate) your desire to do more for your birds, but perhaps there's another way that we can help you do that?
Oh, one more thing - water should be kept as clean and additive free as possible for most of the time. Adding vitamin/mineral packages to the water (especially in the summer) encourages bacteria to grow in the waterers. besides, exposure to light makes the vitamins degrade quickly. Supplementing is best done on the feed or via certain feed additives, then only if needed.
The only thing that I'd personally recommend in the water (especially in the summer when birds drink more) is organic apple cider vinegar, and then not every day and only sometimes to help boost calcium absorbtion, correct gut pH, treat for a bird with nondescript digestive or thriftiness issues, etc. Then sparingly.
