Weird egg, I need advice!

[Aequacheek]

My Sussex hen just laid this in the box. She's a year and a half and appear perfectly healthy, eating, drinking, etc. Her last egg was 2 days ago and normal. She has access to calcium supplement and free range in my yard. I have no idea what that weird second yolk is. Any idea on what could have caused this? The temp have been really high in the past few days, that's the only special I've got :/

 

[dawg53]

Give your hen vitamin D to help with calcium absorption.
Here's a link for you with weird eggs.
https://www.browneggblueegg.com/Article/WeirdEggs/WeirdEggs.html