When they shed the soles of their feet it looks like they've taken off a pair of dirty socks, lol! From around 6 months when their growth rate slows, shedding often occurs in sections and will take several days to complete. It's all perfectly normal, although you can help things along by increasing humidity whilst the cham is shedding. Don't be tempted to 'peel off' any loose skin as this may damage the new skin underneath and could lead to infection.