Unfair treatment at work can encompass an unlimited number of scenarios so it is difficult to pinpoint specific factors which must be present for that to happen. It really depends on what the unfair treatment complained is of and what the reasons for it are.
For example in bullying, that is defined as “offensive, intimidating, malicious or insulting behaviour, an abuse or misuse of power through means that undermine, humiliate, denigrate or injure the recipient.” Whatever form it takes, it is unwarranted and unwelcome to the individual subjected to it.
In constructive dismissal, there has to be a breach of contract and a common breach by the employer occurs when it, or its employees, have broken the implied contractual term of trust and confidence. The conduct relied on could be a single act, or a series of less serious acts over a period of time, which together could be treated as serious enough (usually culminating in the 'last straw' scenario).
In any event you cannot just claim for unfair treatment at work. You have to be able to identify the grounds on which it is happening and pursue it that way. The issue for you is that with less than 2 years’ service you are not protected against constructive dismissal. This wold be the most common way of making a claim for things like bullying, general unfair treatment, etc. So to be able to claim you must really be able to show that it was on grounds of discrimination, which does not require a minimum service to claim. This could be things like gender, race, age, religion, etc.
You have mentioned your age may be a factor here but you must be able to show that there was indeed referential treatment for younger workers when compared to you, as an older one. As you can imagine it could be pure coincidence that you were treated the way you were and it may have nothing to do with your age so some evidence that may suggest they had preference for younger workers will be needed.
This is your basic legal position. I have more detailed advice for you in terms of the options you have on taking this further, which I wish to discuss so please take a second to leave a positive rating for the service so far (by selecting 3, 4 or 5 stars) and I can continue with that and answer any further questions you may have. Don’t worry, there is no extra cost and leaving a rating will not close the question and we can continue this discussion. Thank you