Dog symptoms

Question
I have two dachshunds, One almost 4 and the younger one around 3. Both females and both from the same two parents. The older girl Chacha is very healthy but still on the heavy side(common for dachshunds)with minor or none at all problems through-out her lifetime. The younger dog Koko on the other hand is very very problematic. I am worried about her, but my vet says it is all common, PLEASE I need a second opinion. Koko is very thin especially from the waist, please keep in mind Chacha and Koko have the same amount of exercise and diet daily, she suffers from seizures weekly since about she was 1 or 2. We live in Laredo, Texas which if you dont know is very very hot. Both dogs spend a lot amount of time outside with plenty of water and of course can come inside and sleep inside every night. This is not all of Kokos problems, she suffers from drastic sun spots, although Chachas coat is very very healthy Kokos suffers from loss of hair, Pimple like bumbs and redness all around the back area. With these 3 problems that Chacha does not have, what are we doing wrong with Koko. I hope you have a conclusion or something we can maybe do to help Koko. Thank you, I hope you can help

Answer
Well first of all, overweight doxies are only "common" as you put it because they are over fed and fed the wrong foods. Dachshunds should be thin, and especially around the waist area, so Koko is actually an ideal weight.

Then my question is what do these dogs eat? Most skin problems as well as obesity stem from bad food choices. Skin and coat problems are almost always traced back to diet. One dog might digest their food drastically differently than the other dog. One could have an intolerance to the same food the other dog does well on.

Tell me what you feed, including all table scraps etc. and I can help you better.