DERMA-IONX is helpful for many skin conditions. It is an oral homeopathic product which stimulates the enzyme systems in the body that aids the skin and helps with assimilation of nutritional components in diet and supplements. What sets it apart from most homeopathics is that it is in an oligotherapeutic mineral base which has had a charge added to it.
Initially I would give a half dose of DERMA-IONX on the breakfast and supper food. After there are signs of improvement you can give a whole dose once a day. I would also give Probiotics to aid the immune system. OMEGA 3,6,9 is also helpful in soothing irritated skin and improves coat quality. The water you give should be filtered.
Diet can also influence the skin. Sometimes the flavor even makes a difference. I would choose a grain free fish or turkey food since these are considered to be cooling for inflamed skin according to Chinese food therapy. Beef is neutral. Chicken, lamb, and venison are warming.
Where are the red spots located on the body? Do you bathe your dog?
Have you Googled side effects of Apoquel especially if used for longer than 4 months? Since you have not solved the problem yet, it is time to consider a different approach. I would also consult with a veterinary chiropractor. It sometimes helps with allergies too.