hi and welcome to the forum!
would you please answer to "trouble in the enclosure" questions ( sticky thread) and post your answers here so we can help you better. we also need a better pic of his eyes in better lightening so it is clearly visible what is it.
you say you have 2 of them, but just one is sick, is it right?
it does seem swollen around his eye as far as i can see, so that is what you need to get melafix ( fish medication, usually in fish section of the store), do a solution according to the instructions. use it for everything - spray, papertowels and soak a frog in that for 20 min once a day.
as well you need to set up a hospital set for a frog to live in until it is healed. it should look like that - wet paper towels on a bottom, all 4 sided covered with something from outside. uvb for a day lamp ( or that new exo terra ozone is even better) put some plant inside ( artificial) so a frog won't feel too miserable.

do all that and watch him, if it is not getting better in 3-4 days it is time to contact vet who deals with frogs, you might need systemic antibiotics or special eye drops.

we'll go through your answers to "trouble" questions when you post them. good luck!