Sorry I’m no expert for sick chickens at all. Just know a few basic by reading about it. Only once I had a sick chicken with diarrhoea which was not from too many grapes. 🍇
Maybe Aart can tell you more if you tell her more about eating / crop or perhaps 🤔 @Eggcessive ?
The egg without shell has nothing to do with not enough calcium in her feed. Chickens in a flock that don’t get enough calcium lay soft shell eggs all the time. Its allways good to give oyster shells on the side but extra calcium in the feed is not the solution for one egg without a shell...
The sudden warmth might cause stress. 🤷🏻♀️
I do hope this is just a temporary issue. :hugs
But don’t stop giving fresh water. Provide shade and a very airy coop when its warm. Mine like to take a foot-bath when its warm 🥵.