Sick non-laying leghorn

[DustyChick]

I'm a little worried about my leghorn. She's a little over a year old and isn't laying anymore. She started laying August 2019 and stopped in December 2019, right around the same time my other 4 girls stopped for the season. The rest of my flock started back up again in February. She's my youngest & smallest bird, so I just figured she might need some time to get back into the grove. But yesterday she was acting weird-puffing up & hanging out by herself. She refused mealworms but gobbled up a few grapes. Her poop is greenish, white & runny. I isolated her last night & she's acting about the same today.

The only change I can think of is I opened a new bag of food Saturday evening. I feed them Nutrena Nature Smart Organic Pellets. Any ideas?
The picture with the Buff bum is from February, the other 3 are yesterday. Thx!

 

[RumneyRoost]

Have you checked her crop? It should be full when she goes to roost at night, and empty in the morning.