Partially Brown eye

This is one of my other cats her name is Boba She's around 5 almost 6 years old and I've had her since she was 5 weeks old From what I can remember she's almost always had a little speck of brown in her left eye Today I noticed it looks a lot darker and more covered then it had been the last time I really looked at her eye. From what I've read up on this could be a number of things but I'd like to attempt to narrow it down The first two pictures are the newest and the rest are older I do work alongside vets so I'll be able to take her in and get a more conclusive idea on Monday when I go back into the clinic but I'm just curious

Hello - yes this is definitely a concern but the question is, how quickly it should be seen.  Possibilites do include tumours and clotting disorders so, particularly because this has changed recently and rapidly, we would recommend getting it triaged immediately by your veterinary team.