Yes, if you have the wherewithal to develop your own B&W it is usually better
Labs often place a number of B&W films into the same developing tank (sometimes even of differing sensitivity, or ISO) to save on their time costs. The exposure latitude of B&W film means they can often get away with this cheap trick
One would need to study the negative, but, in your case, i suspect the problem is one of an incorrect "fix"
This forum has several dark room specialists - maybe they might happen along and be able to share their thoughts
it would be very difficult to assess without knowing what developer they used. i use pmk pyro and my ilford hp5 negatives, for example, are yellowish/green, but they are meant to be that way. the only thing that concerns me with this neg is the uneveness of the 'tint'.
whether the lab develops 4 rolls or 1 roll in the tank, there really isn't an issue as long as the ml/h20 is multiplied. thick or thin negs aren't really indicative of development procedures, but of exposure while in the camera.
does the neg have the uneven tint when on a light box or held up to a sunny window?
if you scan B/W use RGB mode instead of gray scale, you get some color tint depoend on scanner, software, density of the negative...it not because negatives have litlle green colour (400 ASA Ilford b/w film),green on neg should become red on print.
it not wrong scan B/W use RGB mode, actual, if you know how to manage Hue and Saturation while you're scanning, you can gain more detail and contrast control than use gray scale mode. after you finished the scan and open with photo editing program you have convert the RGB to Gray to get B/W photo. use PhotoShop?