Doesn't look diseased to me either. Like what Paul said, it may be because of maturity. But some hostas, take 'Jewel of the Nile', for instance, are more unstable than others and their colors can change drastically from one year to the next, usually an eye or two at a time. But whatever the reason for your color change, it doesn't look diseased. The second picture kind of looks like the hosta may be getting a little more sun than it may like, the color on some of the leaves look a bit faded, but I don't know what kind of light it's in if that may be the case. I have 'Elegans' that gets a bit more sun than it ought to get, but the hosta does well there, it just looks a little ratty and faded by mid-summer.
