I've never had that problem, Alina - guess I've just been lucky . It may help to sponge the leaves with just plain water and keep it cool. Sorry I can't help much more than that - none of my plants have ever suffered with it. . What I would say though is don't use those leaf shine products as they block the plants pores. Why someone invented that I'll never understand.
Thank you as well Emma, I feel very proud of Archie now and I promise to give him a bath more often now !