Pension fund purification?

My pension was set up with a generic fund initially and gained value.

I then instructed my pension be transferred to an Islamic fund.

By the time it was moved to the Islamic fund it had already gained some money from the generic fund.

How do I get rid of this potentially haram money that’s sitting in my Islamic fund investment? I don’t think I can withdraw it as it’s my pension fund.

Can I just give the equal or extra amount in charity with the niyyah of purification?

Also do I give the difference of the current value and my original investment OR the difference between the value it reached in the potentially haram fund and my original investment?

E.g. it gained £100 in the generic fund but after moving to the Islamic fund it lost £80 so now only £20 gain from original investment. Do I give £100 in charity or just the £20?

@Mufti_Faraz_Adam @Mufti_Billal salams do either of you know what I can do in this situation?
Aside from this, is all my pension money halal? Do I need to do anything with regard to purification? It’s the HSBC Islamic fund.

I just want to be relaxed and not have anything on my mind that I would need to do in 30+ years time Allahu alim.