Hi gerardine. It could be the weather. I have a couple that are almost into autumn mode!
Alternatively could the bottom leaves be suffering from slug/snail damage?

Hi. Don't worry about that hostas sometimes shed lower leaves. I have a couple in the ground that do this I just cut them off, hostas are very strong plants. I dig mine up when they get too big and split them up, though sometimes the don't grow their leaves as big next time round.