Unfortunately I don't understand French, so I can't read what's in the picture or the description. From the image it looks like it's a collection of seeds and grains, which in the US would be called "scratch" and is meant as a treat, to be given in small amounts, not as their main feed. The main...
At this point any kind of proper chicken feed would be better than what they are currently eating, even if it isn't chick starter or turkey feed. Chickens need a balanced poultry feed that's formulated to already contain everything they need, without you needing to supplement with anything else...