Looks like several possible problems...

slugs are certainly a possibility
cold damage from the strange spring weather

I think the brown spots are a fungus (I scanned an article regarding secondary fungal infections in hostas a few weeks ago, meant to go back and read it and have not done so) that are opportunistic. They happen on already damaged leaf tissue and do not need to be treated since they would not occur on a healthy leaf.

As far as them shrinking, I would guess there is either a lot of root competition for water/nutrients or possibly voles have eaten the roots. I would lift one of the really struggling ones and see what is going on under ground.

Just my thoughts off the top of my head...

Alexa

i agree with the above... but ....

what time of year was it taken? .. it looks like a late summer TIRED hosta leaf... that isn't properly watered in August ...

what is the watering regimen?

the rust is irrelevant.. if you get the slug population in control .. then the rust has no means to enter the leaf... its just a result of bruised and battered surface ...

slugs can be controled with 10% ammonia or vinegar... check the FAQ's and/or use the search function for more info than you need ...

ken

this is a current picture of the leaf ken. He said as the season progressed last year there was not much left of the plants by fall and plants nearby were fine.