Could this be because of heat and more water consumption, or could this be a sign of some health problem?
No. It's where roosting chickens will do most of their elimination. If you surf arund in the Coop Design area, you'll find that it's common to design a roost to allow for the heavy accumulation of manure that will be under it. Whether that be a geometrically complex roost that will accordion up to allow for a shovel and scraper underneath, or as simple as removable pans underneath. But under the roosts is where the "stuff" builds up most heavily. Take a look at, maybe reconsider, your cleaning schedule/regimen, consider the pan idea (it may be your simplest solution). And while, yes, it is naturally the dirtiest part of the coop, consider your ventilation, and whether it is sufficient to remove moisture from the coop in general.
Quote:I had wet bedding under the roost, not solid poo, and it was a sign of health problems. My chickens drank lots of water for reasons other than heat. I do think it could also be related to heat and drinking more.
It is really difficult to give you a definitive answer. We'd need to know: how many chickens you have, how large is the coop, can rain get in, etc. In the mean time, you can add ag lime to that area to absorb the moisture and knock down the smell..... after you have cleaned it out.