We have had a tiger salamander that we found for three years. Over the past month he is shrinking and seems to be drying up. He is lethargic but still eats. He used to hide in the water under the rocks but now he lays on top of the rocks and tries to climb up the glass. He used to look plump and healthy but now looks sickly. One pet store said he might be getting old and another said he may have worms. Any thoughts? Thanks.