I think I have managed to solve this problem.
Where UTC is the column of variables to group medians by, RMS, ZeroPEak, PeakPEak and SEL are columns to find median of.
omedian = @(x) median(x,'omitnan');
medianByRec = varfun(omedian,Filtered,'GroupingVariables','UTC',...
'InputVariables',{'RMS','ZeroPeak', 'PeakPeak', 'SEL'})