I am not sure what has happened to my California Poppy. It has been staying like this for 2 months, no flowers at all.
Wish I could help, but I have no experience with this plant. Also, it is illegal in my area to be growing any type of Poppy, (or Marijuana). Yes there are different verities of Poppy which do not produce opium. So nothing wrong with growing them in the garden - But our authorities don't have any horticultural knowledge. So they just need to see it only once, and you're done... Which just gave me an idea! Why don't I drop some Poppy seeds (with the help of a quadcopter drone) - Over my neighbor's garden. Then report her to the authorities after a month! But in order to do that, I must get a better understanding of this plant first. So I hope other members over here quickly help you out. While I shall be watching this thread with great interest!
These aren’t poppies unfortunately sh. This is just the name. They are weeds here. No idea what is wrong with yours. My guess is that there is something with the roots. Yellow leaves are often a sign of water problems. Yours seem to be well watered though. Maybe do not overwater and see if it starts to grow better.
I planted for the very 1st time some California Poppy seeds earlier this year and they have flowered from the beds not in pots...Planted various seeds this year and some success some disappointments..can blame too dry too wet too cold too hot...weather and water I am sure does make a lot of difference ..sometimes it is hard to get it right...yellowing and lack of growth the plants are not happy for sure....how about moving a few over to the the direct ground...maybe some fine grit added as well....
Yellowing leaves can also mean that the soil is depleted in Iron. https://forestry.usu.edu/trees-cities-towns/tree-care/causes-iron-chlorosis
I have the impression that California poppies don't like to be moved. I think you sow the seeds directly in the ground where you want the plants to grow. My experience with them has been that once you have a flowering plant & allow it to go to seed, you'll have California poppies ad infinitum. Until you don't. Of course.