I recently developed my first roll of 120 fp4 in years. Straight away I noticed that the film base has a strong purple cast. At first I thought it might had to do with the different format although that doesnt seem likely because as far as I know 120 and sheet film are exactly the same, right? (Have used fp4 in 4x5 until now) However, while browsing through my negatives I noticed that my fp4 4x5 negatives also have developed a slight purple hue over time, that is, older negatives are neutral and more recent negatives are more and more purplish. Im using a 5 litre bottle of Amaloco x89 extrafix (with at least 3 litres left). Previously I used Ilfor Rapid Fix and never ran into any problems. I guess this means that my fix concentrate is deteriorating and that I should throw it away? I fixed the 120 film for about 1:30 min with the clearing time being aprox 30 sec. (I checked this afterwards to make sure I didnt underfix the film). I haven't changed my washing method. Will the purple cast cause problems in the future considering that I fixed the negatives long enough? Should I slightly re-fix them in another fixer (and risk overfixing)? Thanks in advance!