strange defects (4-5 spots in a line) in the center of 4x5

[dazdraperma]

Hi all,

just started LF today. Ilford HP5+ 400,
developing:
1. distilled water
2. D76 (stock) at 20°C
3. Ilfostop (1:19) 30 sec
4. Ilfofixer (1:4) 5 min
5. tap water to wash off
6. Photoflo (5ml on 1000 ml

Problem: all of my developed films have a strange defect: 4-5 dots, on a straight line in the center of the frame (along the short, 4" side). Especially well visible on a film that I (unintentionally) failed to expose but developed in a usual way.