Thanks for the answers to my questions.
Your tank temperatures are good as is the diet. I usually recommend a dish of calcium in the tank for geckos to ingest since the Nutrobal will not contain sufficient amounts for them. More on this below.
I also prefer an under the tank heater since they tend to respond to this better than the reflector lamp.
So, just a few husbandry issues which you might address.
When faced with a situation like this in a gecko, there are usually going to be a few possible reasons for his decreased interest in eating:
1. Possibly an internal parasite problem which is why I asked if you'd had a fecal (or a stool sample) checked.
2. A virus
3 A bacterial infection.
4. or possibly a partial blockage even though he's passing stool. You didn't indicate what substrate you use but if it's sand or bark, then a partial obstruction should be included on the list. I prefer reptile carpeting or paper towels which prevent a blockage from occurring..either partial or complete.
It's not always easy to determine which condition might be responsible for this problem without a physical exam, though.
But there are several at-home, first aid things that you can do for him which might get him eating again.
1. Soak him in a 50/50 solution of warm water and pedialyte (or diaralyte) up to his mid leg for about 15 minutes. This will help with hydration.
You can repeat this procedure once a day if necessary.
2. Place a dish of plain calcium in his tank; a calcium deficiency might contribute to shutting down his system.
3. Supplemental feeding with human chicken baby food mixed with a pinch of the calcium. Drop this mixture on his snout several times a day; he should lick it off.
Hopefully, this will be enough to stimulate him to eat but if it doesn't, then he may need to be seen by a reptile vet. If you don't know how to locate one in your area, this LINK
may help. I would also suggest that you take a stool sample with you so that it can be checked for parasites...this actually isn't a bad thing to do anyway.
I hope this helps and I wish you the best in getting Gordon back on track. Deb