If you started copying a Trader before he/she has become a PRO, the commission for the open investment would remain 5%. This commission will not change until the end of the investment. You can check it in the card of this investment in the application.
However, if you or the Trader closes the investment, next time you invest in this Trader, the commission will be the one the PRO Trader has set.
You have invested in a regular Trader (the commission is 5%). While your investment was open, a Trader has become a PRO Trader and set a 25% commission. You have closed this investment with profit, and the Trader has got a 5% commission. You have decided to invest in this Trader once again. This time the commission this PRO Trader will get is 25%.