What you are seeing is not anything you are “doing wrong” per say. This is a spray tan, about 3-4 days old and what you are seeing is the tanned dead skin which is fading, and exfoliating off.
When you see your fresh spray tan crackling between day 3-7, this is more related to the skins exfoliation rate, every persons skin exfoliates at its own rate. Not all body areas will exfoliate at exactly the same rate. Dryer areas such as legs often exfoliate very fast.
The fix is to exfoliate the skin “Before” it gets to this point and respray, or use a light touch-up coat of solution (this can be applied by hand) or a lotion or mousse or aerosol containing DHA to add some touch – up color between full the body spray sessions. In the winter, when skin is dryer, and air is less humid, you will often find the tan fades faster. Other factors that would cause dehydration of the skin would be menopause (the drastic inconsistent change in hormones), swimming in chlorine pools, the ocean etc.
To exfoliate, use an exfoliation mitt and schlepp off dry skin while standing in shower or tub. Exfoliation will help you prep the skin to rebuild the color, and will extend your tan a few more days until you can do a complete through exfoliation and respray session.
There are a number of things you can do to slow this crackly process again, so the tan wears longer before it reaches this point, but they are also limited by the condition of the skin as well.
Pre-tan Prep (good exfoliation steps),
Moisturizer use twice daily or as needed, and most of the time you will need to switch to a good old fashion body butter instead of products you purchase in drug stores
Request a Hydration Spray from your spray tanner (liquid body butter)
Drink a lot of water daily
Light exfoliation durning the tan fade process, with touch-up DHA product use like a self tanner (ask you spray tan artist what products they recommend)
Adjusting other skin care steps that may be increasing he fade rate (hair removal from legs for example)
Switching to a higher moisture product during dry times of year, or for those with very dry skin.
I hope this helps answer some questions of why your spray tan isn't lasting as long. I am always providing as much education to my clients on how to learn what your body needs (9 out of 10 times) as far as skin hydration to maintain the "Sunless Lifestyle".