We have had two egg bound hens in the last few months and I’ve noticed some of the egg shells seem to be thinner/weaker. We use Kalmbach Layer feed which has 3.5% calcium and we offer oyster shells at all time, but I rarely see them eat it. What else can we do to increase their calcium? I asked about adding liquid calcium to their water and it seems that might not be the best idea. Any other suggestions?