Hatchling kings not gaining weight

I am screwing this up?

Temps are what the Kingsnake care literature says - mid 80's hot spot, low to mid 70's on the cool end. I have a new temp gun, and another digital with a probe, so those readings should be accurate. Plenty of hides in each tank, and clean fresh water.

These snakes showed up in our kitchen weak and dehydrated on Oct 3.
Dusty: Weight: 12 grams 12" long (measured as best I could)
Sticky: Weight: 12 grams 13" long (good measurement)

First feeding, a pinky for both on Oct 6

October 9
Dusty: Weight 13 grams
Sticky:Weight 14 grams

October 13
Dusty: Weight 12 grams (back to 12??)
Sticky: Weight 13 grams (They each lost a gram, and are back to their original weights!)

After weighing, each fed a pinky

I don't want to overfeed, but maybe I'm being too conservative?
We bought two more pinkies, just slightly larger to freeze. Maybe I should these f/t feed again in five, rather than seven days?

The snakes were lethargic when first found - not in great shape. They have been doing very well since then - so until I weighed them, I was SURE they had grown. I can feel the strength in them, they are inquisitive, and they look good! They don't look thin. They actually seem to enjoy being handled. I was shocked to find they were back to their original weights!

I wouldn't be concerned. essentially they've had no change in weight after a single feeding. I would start offering every 5 days.

You can feed your King a prey equal to 1.5 times it's girth size 2 to 3 times a week however do not expect any huge weight gain until the animal start eating more meaningful prey item such as fuzzy.

The most common mistake with new colubrids owner is that they do not feed enough not realizing that colubrids have a high metabolism and that a pinky is insignificant.

I feed my young colubrids 10-15% of their body weight every 5-6 days on average. Sometimes they eat a little more, sometimes a little less. I do agree that you'll see more significant weight gain once they're eating larger prey.