What makes you think it could be something to do with the feed?I wish I knew. I'm running into the same issue. I have never had less than an 80% hatch with my own (the lowest hatch rate included a 10-hr power outage and was just over 80%), and most of my hatches prior to this year were 100%. Even with shipped eggs I've rarely had less than an 80% hatch. Yet this year I'm struggling to get 50%. Most all of the eggs make it to lockdown, and several even make it to external pip, but then that's it. Yet those that do hatch normally are active and seem just fine. I'm beginning to wonder if it doesn’t have something to do with the feed.
I'm quite interested in that because I'm starting to suspect weird issues with feed as well and have noticed lots of people mention it, not necessarily in relation to hatching but in all sorts of different threads.