Help! Weak floppy pullet

[Amurr]

My birds were doing perfect this morning. I gave them a head of ice burg lettuce to decimate and three hours later one of my Colombian Wyandottes was laying in the bottom of the run. I brought her in the house, put her in the empty brooder box, dipped her beak in water.
She's weak, can't stand, tips toward. Legs seem tense. Doesn't want to hold her head up.

She's 10-12 weeks old, and up to now has been in perfect health.

 

[camella]

Could it be coccidiosis? Are her wings droopy? Did you give them medicated starter or a coccidiosis vaccine?

 

[Amurr]

Could it be coccidiosis? Are her wings droopy? Did you give them medicated starter or a coccidiosis vaccine?

It's possible but Im not sure how likely. I clean their space a great deal and they've been on medicated starter since they came home.
She was in perfect shape until she collapsed. Eating, drinking, running around. No poopy butt or droopy wings. No visible injury. I'm at a loss

 

[camella]

Do you have Corid? There are many great threads on here with coccidiosis treatment protocol. If you have Corid, I suggest “drenching” the one presenting illness and give the others Corid water, just as a precaution. Coccidiosis strikes very quickly and will take out your whole flock before you know it.