Have you found a local vet who will let you bring in some fresh droppings? They could be collected overnight in a dog crate, or by placing a tarp of board under their roost spot. I would not give any laxatives to a chicken, especially Exlax.
If you cannot get droppings checked with a fecal test, you can buy Valbazen or SafeGuard liquid Goat Wormer from a local feed store. For normal worms give 1/2 ml of Valbazen orally for a normal size chicken, 3/4 ml for a very large hen or rooster. Repeat the dose in 10 days. If you use SafeGuard, give 1 1/4 ml for a 5 pound chicken or 1 3/4 to 2 ml for a very large hen or rooster. Repeat that in 10 days. For very serious worms such as capillary, gapeworm, or tapeworms, the dosage or number of doses may be increased. But for round worms, the ones you can see in the poop, the regular one dose followed in 10 days is good. If you have many birds, Wazine 17 used in the water for 24 hours 1 ounce per gallon will work, but it does not get any but roundworms.
