I had them already, I bought them since they where 18yo obviously to replace aging players at the time. Christiansen was a ST but he was fast trainer and I paid 40T in a bidding war. He didn't perform well at all the first 2 seasons 5 goals per season. I gave him One on One SA but nothing, he was still young and I gave him a new AMR position to see if he would be any better but no. At the age of 21 I had to let him go despite he could easily play 2 or 3 more seasons as a starter based on his rating.
Fischer was a AMR/MR/DMR (DR after the update). I paid around 40 T for the guy too. He wasn't that bad in the first seasons or so but he did not score enough for an AMR, gave him shadow striker SA and nothing really changed. I used him as a reserve DR last season but he was terrible in that position and felt very un-natural. At the age of 22 I had to let him too despite all my efforts to enhance their performance.
This guys where never amazing and even thou I could save some Tokens for 2 more season I had to get rid of them since they were holding my team back.
In your case I hope it was just a bad season overall for the team and not the players fault. I hope and think they will return back this season. In my experience good players no matter what position they play, remain good. Of course some seasons are better than other. what kind of formation do you use?