My Great Dane appears to be dehydrated. . .but shouldnt be.

I have an almost 4yr old Great Dane and the poor thing is always plagued with numerous health issues, repeatedly and constantly. Im not sure which problem is worse. She gets dry spots randomly all over her body, her nose is so dry to the look and feel, that it feels like course sandpaper and looks "cracked". Her eyes get so bad they too appear to be dry and crusty, and at times give her eye sockets the look of being hollow. She also gets ear infections a couple times a year. She has been to the vet numerous times and been treated with topical and pill form antibiotics, ear cleansers, daily fish oil pills. the symptoms clear up but always return at any given time. I make sure her water bowl is always filled, even when she's outside, Im faithful with her daily fish oil pill, and we also use the topical antibiotics when the rash starts to surface. When symptoms are full blown, she appears to be extemely dehydrated. I now have a new problems, that she hasnt seen a vet for yet. She had a spot on her chest that had the look and size of a pencil eraser. We thought it was gone but it actually grew to appx 2"x2" and for lack of better words, has the look of a brain. It does not seem to bother her is any way, she does not lick or scratch it, but I fear it may be a tumor. Does anyone have suggestions on how to keep this dryness under control, and does this new spot on her chest sound like anything you may have experienced with your dog.

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