Cockatiel not growing feathers properly and eye issue

I have a female cockatiel, she’s about 1.5 years old. The problem is with her feathers. She started molting when she was around 4 months old, and since then she hasn’t been able to properly grow them back. Whenever new feathers grow and she tries to fly, they break. Her weight is about 80 grams. I only give her a seed diet (mix of canary seeds, sunflower seeds, etc). I tried giving her flakes, fruits, and vegetables, but she doesn’t eat them except for corn. She has never had any injuries and she is a really happy bird. Loves calling me and spends most of her time outside the cage with me. I keep her on the ground so that she doesn’t fly, because if she is on the table or bed she tries to fly and I want to prevent that. Another issue is her one eye, it’s red and watery. We don’t have bird vets in my country, so I really need advice on what might be going on and what I can do for her.

Hello there I can hear that your cockateel has several problems: 1) feathers keep breaking 2) eye change- this can be related to injury from broken feathers when grooming, as feather shafts are sharp.  However, there are dozens of potential reasons for it. 3) unable to exhibit natural behaviours - for a bird, this involves the chance to fly.  Cockatiels also live in groups in the wild, so mental welfare may be struggling. It sounds to me that at this stage, a vet - bird specialist or not - does need to check your bird as they are showing signs of ill-health.  If they do not have the information they need, they must find out or pass you on to someone with the appropriate experience and it can pay to be very clear about this. Indeed, it seems possible that all three of these problems are caused by underlying lifestyle factors.  This is not about fault; It is frequently not made clear what an appropriate diet for  a cockatiel should look like.  Information can appear conflicting; pet-shops can still give the impression that birds will be ok on a diet of bird-seed, which we know not to be the case. Indeed, the feather problems could well be linked to nutritional challenge.  I also wonder whether your bird is getting adequate exposure to UV light.  Your vet, bird specialists or not, should be able to talk you through the housing and care required for a cockateel - the Royal Veterinary College London have produced a good online fact-sheet about it.  Meanwhile, a veterinary assessment is imperative. Please do proceed with some degree of urgency on this one.