If you have gravity tanks and syphon feed
soap, its possible you have debris in one of the
soap solenoids allowing water to flow back into the
soap tank diluting the mixture. Especially if your hot/cold water float tank level is higher than the
soap tank level. Although, if this is the problem, it will take
soap longer to get to each bay since the
soap supply lines will have pure water in them. Then about all you can do is inspect each solenoid to find the culprit....
Do the easy stuff first like suggested....Then....Start checking
soap solenoids...