Tetenal have a few different C-41 kits. The developers differ as Mono, 2-part and 3-part chemistries and have varrying degrees of capacity (regeneration rate), smell and health-safety quality (the so-called Environmental or clean air lines) and even process--- alongside the C-41 there are a few different C-41-RA or rapid access processes. One should do some standard colour tests. Some of the different developers demand different starters and some of the different bleaches need a starter and some don't. There are a few different bleaches, fixes and bleach-fixes in Tetenal's program. Bleach is never just bleach as the different bleaches will indeed result in different final mask colours. Here too one should do some tests for retained silver.
Originally Posted by Poco
One does not need to purchase "real"(tm) Kodak control strips but can make/design one's own using a colour film of your liking. If the process chain is calibrated to produce what you consider good output and you calibrate to test strips that produce in the chain good output then they are sufficient and can be used to check the process and, especially, chemistry changes.