Why would the Collar and Cuff Scrub (SCR1) leave yellow marks on garments?
This product works really well when used correctly. The SCR1 should be applied, scrubbed on to the collars and cuffs of shirts and then laundered before the SCR1 dries, otherwise yellowing is likely.
However, if you have always used this product and have never had an issue with it before there may be another reason for the yellowing. The pH of the shirts may be off. Is there enough sour being used? When washing clothes in a commercial laundry the detergent is more alkaline. It’s important to clean, rinse, and add a sour to neutralize it. If the clothes are more on the alkaline side and if heat is added, the clothes could get discolored. Also, make sure that the garments are being rinsed thoroughly. If there was not enough soap taken out of the garments, that could also discolor the clothes. Try 2-3 rinse baths for 2-3 minutes longer- and test the alkalinity.