leopard gecko looks gray/weak

Question
Our leopard gecko suddenly looks gray in color (except the head) and seems very lethargic and weak.  It is still eating small crickets but is not chasing them as he once did.  

Cage heat seems to be well regulated with an under talk warming pad.  

I do not yet have a cave with moss for shedding - working on that today.  I keep a small dish of clean water in the habitat at all times.  

I supplement with calcium powder.  

The gecko just seemed to take a very sudden turn for the worst and I'm not sure what happened/changed.  We've had the gecko for 3 weeks.

Thank you

Answer
Hello Michelle,
It sounds like a shed coming up though.  I mean the gray coloring.
You do need to get a cave with dampened moss to help with shedding.
They do tend to get slow & lethargic somewhat when getting ready to shed.
Are the crickets appropriately sized?  
Do you have a basking light as well as the undertank heater?  They need a hot spot of around 88-90.  

Keep me posted on him.

Tracie