Deterioration of negative highlights? Please advise.

[batwister]

After looking through some old negatives, I decided to give a set of particularly bad ones (marked 'burn') another chance. This was a roll that had been sent off to my lab for development and received N-1 in XTOL.
At the time they were put in my throw away batch for aesthetic reasons, but I hadn't noticed this until now:



They have been stored exactly the same as all my other negatives - about 30 rolls in this box - and are the only ones with this problem. Several of the other rolls in the box were developed by the lab exactly the same, and shot on the same film - Delta 100 rated at 50. However, the roll in question (from which the attached image is sampled) was sent off with my first roll of Delta 400, rated at 200. Is there a chance they were developed together by the lab? Or is this something to with storage - possible condensation/heat? As I say, I didn't notice it at the time and certainly would have.

 

[Bob Carnie]

If I am not wrong , what happened is this film was roller transport processed and you are seeing scratches on one of the rollers in the tank.

I do not think this is dip and dunk or hand process or jobo process.

I am assuming you are referring to the two lines of minus density across the middle of the film.

 

[Bob Carnie]

Or if you are referring to the mottle in the upper sky which usually is an initial lack of agitation problem.

 

[batwister]

Hadn't thought of that. My first impression was having sent off this roll (Delta 100) and a roll of Delta 400 together, the lab had developed them both for 400 - i.e. 24C for 9 mins, where Delta 100 would be 18C for 6 mins. The roll of 400 came out fine.

EDIT: Oh, I see what you mean by 'lines'. They are in fact telephone wires. I'm referring to the sky, yes.

 

[Bob Carnie]

Well the mottling looks like foam or insufficient agitation .

Hadn't thought of that. My first impression was having sent off this roll (Delta 100) and a roll of Delta 400 together, the lab had developed them both for 400 - i.e. 24C for 9 mins, where Delta 100 would be 18C for 6 mins. The roll of 400 came out fine.

EDIT: Oh, I see what you mean by 'lines'. They are in fact telephone wires. I'm referring to the sky, yes.