How old are they? These symptoms make me think of either Coccidiosis or worms. If they are young, Coccidiosis is more probable, though the symptoms described don't fit it exactly. Worms can affect chickens of all ages. Do you hens feel thin, or lightweight? This would be another indicator of worms.
Stay aware for any other signs of disease. Diarrhea and lethargy, as well as a pale comb, are just general signs that a chicken isn't feeling well. Still, I'd advise you to treat for both Coccidiosis and worms.
The treatment for Coccidiosis is Corid liquid or powder. The dosage for the liquid is two teaspoons per gallon, and the treatment for the powder is 3/4 teaspoon per gallon, given for five days. Replace the water daily, and don't give any dairy products, apple cider vinegar, or vitamins during this period.
If you see improvement after the Cocci treatment, you don't have to worm them. But, if you see no improvement, you should deworm. Don't deworm right after treating with Corid; give them a break of a week or so, while giving them probiotics and other immune-system boosters. This is because worming can be hard on a chicken's system.
Some good wormers are Valbazen and Safeguard. Safeguard (a goat dewormer that can be used for chickens) is the safest, but Valbazen will do the job just as well. I personally used the Worminator (
http://www.twincitypoultrysupplies.com/store/index.php?main_page=product_info&products_id=584).
Hope this helps! Keep us updated if any new symptoms appear.
