My suggestion would be to try a different type of earthworm. I have a couple different species of fire salamander, and found they both prefer the much larger "nightcrawlers" I get from a local bait shop as opposed to "trout worms" available at Walmart or smaller earthworms found in the yard. The nightcrawlers are huge, sometimes over 6" long, very fat and "wriggly", the fire salamanders simply can't resist.
Also, they are more economical and quicker to feed them, because 2 large worms is enough to satisfy the most voracious of salamanders most of the time.
On a side note, I've never had any issues with reduced appetite keeping them at 70-72 degrees, I know it's a bit on the hot side, but I don't have a basement and don't like blasting the AC. I had an AC issue earlier this week with a frozen condensor which caused the temp to spike to 79 degrees inside
one day, the fire salamanders were not as active as usual but they are still eating like pigs, so I'm skeptical of the temps in the 60's being
required to get them eating well. Fyi...mine are S. Salamandra and S. Gallaica.
Also, is this a wild caught or CB salamander? It's fairly common for the WC ones to have issues eating after the stress of shipping, poor keeping by wholesalers, possible parasites/disease, ect. I would be patient, try different worms, and hopefully it will come around soon.