I am definitely not an expert on this - just had my Uro for 6-7 weeks, however she just went through a shed and lost the last little bit of shed on her tail this past weekend. It did turn white and the top "layer" of skin came off. She still has the spikes underneath. So, if this is what is happening it should be okay.
Without seeing a picture, I cannot be much more help!! Sorry!!
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Kelly
0.0.1 Uromastyx - Digger
0.0.1 Bearded Dragon - Spike (Actually Daughters)
0.2 Cats - Smokey & Freckles
1.1 Dogs - Rascal (Shar-Pei/Lab Mix) & Sabrina (Shepherd Mix)
0.0.8 Fancy Goldfish - One Eye & F2 (only 2 named - sorry!!)