Young burms are "programmed" for rapid growth as hatchlings (SURVIVAL). At that age, you might consider bumping up either the number of prey items, or, try a larger prey item. My baby burms/retics/etc. typically get fed 2-3 prey items every 5-7 days depending on willingness to feed for the first year and then I begin cutting back to every two weeks. My largest burm, a 18' female, gets one to two large rabbits a month and that keeps her in tip, top shape. I also supplement with a quality vitamin/mineral supplement every third feeding for all of my burms - more often for hathclings (I do this because I feed mainly frozen/thawed). But, the bottom line is that there is really no scientific evidence to support one regimen over another so you must do what you feel is best. I like to gauge the health of my snakes by overall appearance....I want my snakes to be alert, moderately active, firm and well rounded but not obese.
Hope this helps.
Rob Carmichael, Director/Curator
The Wildlife Discovery Center - City of Lake Forest (IL)