Red eyes are generally not a concern for adult angels. Most breeds will have red eyes, although the gold gene is one which inhibits it. What types of angels do you have? My black lace and smokey both have red eyes; my 2 golds and gold marble do not.
It difficult to ascertain whats going on with you 2 angels. You say the skin near the dorsal is yellow...unusual. Hemorrhagic septicemia comes to mind, but that usually consists of reddish streaks on and near the fins, not yellow. How long have the fish been ill? Have there been any changes prior to the fish showing signs (new fish added, new decorations, new chemicals)? And are they showing any other signs; behavior changes, heavy breathing, glancing off tank objects, eating changes? And azn asks an important question; what are the nitrate levels?
One other thought. How old are they? Some angel breeds will show a goldish/bronze crown as they mature. The color change may simply be that.