It's associated with quite a few issues, pretty contentious stuff; a lot of livestock keepers (of horses, sheep etc) won't touch it.
The correct utilization of most nutrients is dependent on them being in organic form or as close as possible to natural form, and in the correct spectrum (accompaniment of the other nutrients used to digest them). There are many forms of calcium and some are not safe at all.
Taking calcium without magnesium, whatever the form of calcium being taken, is often either inefficient or harmful, and generally hard on the kidneys. If calcium goes in without being in conjunction with sufficient magnesium, it balances itself by taking that magnesium out of the animal's stores. Same as the reverse. This can make it harmful especially in already depleted individuals. It's why supplement manufacturers for humans have now added multiple other nutrients to calcium and magnesium supplements, including forms of vit D and multiple forms of vit C. Long term studies showed it can be harmful to take isolated, purified and overprocessed nutrients, which prompted that change. Since the average commercial feed for chickens is made for chooks that are generally expected to be culled very young, around 2 years on average, long-term survivability on their feed formulas is not a consideration. I believe long-term reliance on those feeds causes numerous deficiency diseases since they only contain basic survival rations, not actually a complete feed for longevity.
Calcium and magnesium need to be in the correct ratio for the body to use them properly and dicalcium phosphate is not the correct form for true health. Like many of the other ingredients in common poultry foods, it's cheap and convenient and will do at a pinch but for the best long term health you do generally have to get something better quality which generally means spending more or learning to mix your own feeds which can be cheaper in the long run but does take more time.
It definitely sounds like your hens need more calcium. Overreactions to everything are common without enough calcium as it coats the nerves, insulates for all intents and purposes... When they become a little stimulated, with sufficient calcium they remain calm but just more watchful, with insufficient calcium they can become hysterical. Personally, I never bothered with trying to handle animals with obviously poor calcium levels if it could be avoided. That's the profile of the animal most likely to die from cardiac arrest, because calcium and magnesium are extremely important for correct heart function. But that's not the most likely end result of handling animals low in cal-mag, most cope since the body basically 'digests' the long bones in order to gain sufficient cal-mag to keep the heart and brain working sufficiently... The real reason I didn't bother is because their over-excitability means more harm than good can be done in handling them, in terms of what they learn from it and how likely they are to react reasonably.
Another thing you can do is offer something like wholemeal bread buns with poppy seed in or on them. Or just the poppy seed added to feed, like a wet mix, so it binds to the food rather than falls to the bottom. While it's quite low in its opiate qualities compared to its pharmaceutical relative, culinary poppy seed can still help soothe fractious or anxious animals. Chamomile can too, rosemary is another nerve tonic, stinging nettle tea or dried leaves added to a wet mix are also great for supplying cal-mag and many other nutrients including protein and vitamin E, but generally just giving them a more rounded diet than what the typical layer feed supplies can help a lot.
I don't know exactly what they're eating obviously, my guessing what they're eating is based on the most common issues with a dietary basis one sees, and it's never one size fits all, so good luck with your experiments in that area if you decide to do so. There can be other reasons why a diet sufficient in the right forms of cal-mag is still not enough, for example intake of toxins robbing the body of its stores, since calcium is used to detox, and illness and injury even of so low a level no symptoms show still can really chew away at their calcium stores.
Best wishes.
