Sometimes yellow or tannish, runny or creamy droppings are just cecal droppings, and normal. So pictures would be helpful. Yellow, watery, eggy, mucousy looking droppings are a different thing. If the bird is acting sick or lethargic, or every dropping looks that way, then a cause should be looked for. Corid is pretty safe, so likely no harm if it's something else (if in doubt, I would treat), but if it's not coccidiosis, then no need to treat for that.