Why the two sources disagree in the first place
The conflict usually feels personal but is actually structural. A care sheet describes an average animal of the species, in an assumed enclosure, written at a particular moment by someone whose experience you cannot inspect. Your vet is looking at one specific animal — this weight, this history, these blood results if they were run, the photographs of your actual setup — and is advising for that individual, including problems the sheet's author never had in front of them. Sheets also quietly age: husbandry thinking on lighting, enclosure size and diet has moved within the keeping lifetime of many animals, and old sheets get copied from site to site long after their advice has been superseded. Some disagreement between the two is therefore expected, and it does not by itself mean either source is careless.
What to ask the vet about the difference
The most productive move is to take the conflict back to the vet openly rather than quietly choosing the advice you prefer. Show them the sheet and ask what in your animal's case drives their different recommendation — an answer like 'for a healthy adult that range is fine, but his weight and that softening jaw change it' is exactly the reasoning you need to hear. Ask what outcome the change is meant to produce and over what timescale, and how you will both know whether it has worked. Ask which parts of the sheet they agree with, since the answer is rarely all-or-nothing. A vet who treats reptiles regularly will not be offended by the question; reconciling generic guidance with an individual patient is most of the job, and their answers tell you a great deal about their reasoning.
Checking a care sheet's credibility
Before weighing a sheet against professional advice, inspect the sheet itself. Is it written for your exact species, or is it a generic 'small lizard' page quietly applied to everything? Does it name its author and their keeping or professional background, and does it carry any indication of when it was written or revised? Does it explain its reasoning — why this temperature, why this lamp — or does it simply issue numbers? Sheets that cite current practice, acknowledge ranges and trade-offs, and match what several reputable sources say independently deserve more weight than a confident page copied, unattributed, across five sites. Notice, too, what the sheet assumes: many are written for adult animals in standard enclosures, and their advice bends when the animal is young, elderly, breeding or unwell.
Making the call, and then watching it
When you must decide, weight the advice that knows the animal — but implement changes the way good husbandry always changes: one significant variable at a time, gradually where the variable allows it, with the results observed and written down. Sudden wholesale changes to temperature, lighting and diet at once leave you unable to tell what helped, and can stress an animal who was coping. Keep a simple log of what changed, when, and what you see in appetite, activity and shedding afterwards; that log is what turns your next vet conversation from competing opinions into shared evidence. If questions remain after that, put a follow-up question to KinsLe's Kinny; he answers using the KinsLe Answers library.