Print problems at Costco. What to do?

I had about 50 pictures printed at Costco. They have never failed me before. I am adept at using Photoshop and have been using it to prepare my prints for at least 10 years. I checked each print personally before submitting for printing. I unchecked their auto levels option, since I had already gotten the images exactly as I wanted. Their site stated that if you have adjusted your prints yourself, to uncheck the box. I have never noticed that box before, so maybe they have been adjusted by their service in the past, but I have not had pictures printed in over a year, so it may be something added since last time I had prints made.

For the first time ever, I got back really dark prints. Unfortunately, I did not check them at the store, and when I got home, I assumed I had somehow messed up. However, when I looked at the photos on my computer this morning, I noticed that a light gray cloud in one of my pictures was BROWN. Even pictures taken in bright sunshine were dark and looked like evening shots.

I did sent the print order early afternoon. I normally send it in the morning. I had some misgivings about sending the pictures for printing at 2:00 as opposed to earlier in the day, but does it make a huge difference? I am wondering if they have not refreshed their chemicals, etc., and that this is their error.

I plan to call them as soon as they open, but any suggestions you have would be appreciated. They are a half hour drive, and I am not happy about the cost to reprint, especially since I think this is their fault, or the time it takes to drive there to pick up reprints. Are they willing to reprint at their expense if they had done a poor job?

Update: I called and spoke to the gal in the Photo Center. She seemed unwilling to admit that the problem could possibly have been on their end. She kept insisting that I must have had autocorrect on, even though I told her that I had unchecked it. I am guessing she just gave the standard, rote answer to complaints. Finally she said to bring my pictures in tomorrow when the supervisor would be there. I am seriously considering having them printed at Walgreens today to compare.

One more update: After getting a few of the same photos printed at Target, Walmart, and Walgreens, all of which were lighter than the same Costco prints, it is obvious that Costco has a problem. I made no changes to the photos, just copied everything to my jump drive and picked a few different random photos to print at each location. I will be taking them with me tomorrow when I talk to the supervisor at the Costco Photo Center tomorrow.