I think your development time is too long. When shooting fp4+ I usually develop for 6 minutes in 1:25 at 20Celsius/68Fahrenheit. The instructions with my rodinal says that for 1:50 at 20degrees the development time is 8 minutes. At the moment I use Rodinal at 1:50 + 4g/L Sodium Ascorbate 20degrees and times for 1:25 dilution. This gives smaller grain. With fp4+ the difference is small, but it's very noticeable with hp5+.(posted 8237 days ago)