If the standard forms two spots means it forms two solute fronts one near the baseline must be due to impurity and the other spot in top is attributed to parent standard quercitin.
In our lab we have used Toluene:Ethyl Acetate:Formic acid (5:4:0.2) for quercetin (quercetin dihydrate) and very slight band was observed at the origin of the sample application other than the parent querecetin peak for HPTLC. But for that band peak to noise ratio in chromatogram was very less and was negligible. It might be depend on the percentage purity of the standard sample.