Probably the heat. The conditions here aren't really suitable for him.
Yep, although if he is struggling in 25C I'd be a little concerned.
He didn't even have to do much running today either.
The next match could be interesting. Temperatures could be around 28C (still lower than average?) so that would make it tougher for him. However, Hernych has played a marathon against Bellucci so he would surely struggle as well. Could get ugly.
More rain and lower temperatures on the way for early next week, so that could suit Toad more, especially if he advances to play Tsonga (who would like it quicker). Dolgopolov looks a very dangerous prospect in this section, though.