If you used a liquid kit, then the sediment was either in your water or in the kit itself. If you used a solid kit, then there is a higher chance that you either did not dissolve everything or that the kit had particles. But, a C41 kit is nominally just as sensitive (or insensitive) to water supply as any other kit. The ingredients are pretty much similar except for the bleach. I use filtered tap water due to a similar problem about 10 years ago. Our water had a lot of sediment which ended up being iron (rust) in the lines.
Filtration through a paper coffee filter should fix this problem, but remember that the particles may also be in your tap water.
PE