You'll probably want to check FSANZ's take on it, but in general I'd expect Pb (and Cd, Hg along with some of the mycotoxins, aflatoxins etc) to be treated slightly differently to the MRLs for agrochemicals, as it's (hopefully!) not something that is intentionally applied to the crop.
My understanding is that the Aus/NZ view is similar to Europe where these would instead be considered as contaminants, but you're probably more familiar with the local regulatory position than I am.
Contaminants like Pb can be more tricky to resolve than a "simple" pesticide issue, as they are potentially related more to natural growing conditions, soil composition etc.
Nonetheless, as a start - what was the actual result, how does this compare to regulatory limit, what is the uncertainty in the analytical method etc.?
Is it a grower with whom you've been working for some time, and do you/they have historical data that can be reviewed to see if they have a history of higher (even if not excessive / problematic) levels of Pb in this crop?
Is this a newly introduced crop using land that previously grew something else in which no problems of this type were observed? Some crops pick Pb up from the soil more than others - for example in the EU the limit for e.g. apples is lower than for strawberries, as a reflection of this.