Sorry to see that nobody replied to your thread! Good to hear she's better.
Pale faces are never a sign of health even in week-old chicks, if they're truly healthy and getting all they need from their diet, they have pink to red faces. Pale faces indicates weak circulation. Once an animal's been raised on a diet that causes that, though, it can be almost impossible to get them 100% --- but they can get about 80%, which is better than <10%.
I'd highly recommend you give them a pinch of kelp per bird per day with their feed as a general dietary additive; it is an endocrine regulator and carminative and contains all the vitamins and minerals in the correct balance. It's cheap compared to other nutritional supplements too, and more powerful by far. You can get it in bulk at feedbarns, produce stores, etc.
It sounds like a cardiac issue to me. A blue face means that for whatever reason, she's not getting enough oxygen (as I'm sure you know). Generally the heart is the best bet when a face goes blue. Regarding the other hen that died, if her comb/face went blueish or gray soon after death, that would indicate heart failure. Animals and humans can live with heart failure for years, even decades, before dying of it or something else. Congestive heart failure is a common disease that many seemingly healthy humans and animals have.
If circulation is bad, the heart is also not 100%; it's all interlinked, and interdependent. There is no such thing as a truly healthy heart in a body showing weak circulation. There can be a structurally undamaged heart, but many, many things can be wrong with a heart, and a body with weak circulation puts more strain on the heart and will eventually contribute to its failure.
Chilli is great for the heart, as are pretty much all hot foods, which poultry love; it's also cheap and healthy for worming them and can be fed every week without harm, unlike many chemical wormers. Some man-made antibiotics kill some gastrointestinal microfauna and flora off permanently, and even taking supplements won't restore them, unfortunately. Your hen may need ongoing help with her digestion. Raw garlic is antibiotic, antifungal, antiviral, etc and prebiotic, so it feeds probiotics; it's also great for heart problems, disease in general, worming, healing, virus control, even external parasites. It's high in sulfur so once the animal's been on it for long enough their blood will poison external parasites too. Also, that sulfur and the other components of garlic are very beneficial to the cardiovascular system's flexibility and the purity of the blood, which is necessary if there's a bacterial infection colonizing a heart valve, for example.
Heart cancer is relatively common in chickens, as are heart attacks; we feed them a diet that cardiologists recommend humans avoid (cooked protein, cooked essential oils) so it's hardly surprising. I would guess your hen had a fairly severe heart attack by the sounds of it. Contrary to popular belief the majority of first-time heart attacks are not fatal, in humans or animals. But it sounds like she lost some heart muscle, since you don't say there were any symptoms of respiratory disease, and it's very possible she may be killed by a follow up episode of heart failure. I would add some cold pressed olive oil to their diet at least once a week; it makes the cardiovascular system more flexible and healthier. Raw oils are vital; olive oil, coconut oil, etc are two of the very best.
Best wishes.
