Hi, noticed these on the bed of my 1955 ford f100 truck are they considered to be rust?

 

Welcome to FTE.
The brown-orange is rust, but is not rust-thru. They could probably be cleaned up with a good wax job.
You also have some stress cracks that weren't addressed before painting, were "repaired improperly or developed after it was painted.

 

Thank you very much for your reply and do you know how the stress marks could be fixed?

 

The trouble is, they are cracks in the metal of the body. There is no easy fix to do it right.
You need to take the paint off down to bare metal, weld them and then repaint.

Are they serious to the structure? Probably not, but I can't say for sure from the pictures. At best, they are blemishes on an otherwise nice older paint job. There is rust developing on the edges of the cracks.

 

Thank you very much for helping me, the problem is that I got more of these around the car.

 

Looks like the surfaces weren't properly prepped before the paint, and moisture trapped in the underlying bodywork has started rusting through.
Or they assembled the box in bare metal, and painted it after, leaving every seam / joint free to rust and that rust is seeping out around the cracks.

Use some wax to clean off the rust, and hopefully seal up where the rust is seeping through, until some future date.

Kirk