Would it be discrimination if my bonus was reduced when I was on maternity leave last year?

[Hungrycaterpillarsmummy]

We get our bonus in April and I qualify for it even being off on maternity leave.
We got an email recently saying we won't be getting the target amount because the company didn't hit one of its targets but increased another portion of it so in the end we will be getting 67% of what our personal target was.

There is an addendum which says our managers can reduce or increase the value at their discretion.
I have a feeling my manager may reduce my bonus but would this be discrimination under the circumstances?

If your contract gives you a bonus based on work done in a year, you're still entitled to part of your bonus. You'll get your bonus for the part of the year you're at work, but not the part of the year you're on maternity leave.

www.citizensadvice.org.uk/work/maternity-and-parental-rights/check-your-maternity-and-parental-rights/rights-while-pregnant-or-on-maternity-leave/rights-while-youre-on-maternity-leave/

Mm ok thanks. So I was on Maternity until 1 nov so looking at a very small sum then :(