We extend the PARSEC library of stellar evolutionary tracks bycomputing new models of massive stars, from 14 Msun to 350 Msun. The input physics is the same used in the PARSEC V1.1 version, but for themass-loss rate which is included by considering the most recent updatesin literature. We focus on low metallicity, Z=0.001, Z=0.004 andZ=0.0005, for which the metal poor dwarf irregular star forminggalaxies, Sextans A, WLM, NGC 6822 and SagDIG, provide simple butpowerful workbenches. The models reproduce fairly well the observed CMDsbut the stellar colour distributions indicate that the predicted blueloop is not hot enough in models with canonical extent of overshooting.In the framework of a mild extended mixing during central hydrogenburning, the only way to reconcile the discrepancy is to enhance theovershooting at the base of the convective envelope (EO) during thefirst dredge-UP. The mixing scales required to reproduce the observedloops, EO=2Hp or EO=4Hp, are definitely larger than those derived from,e.g., the observed location of the RGB bump in low mass stars. Thiseffect, if confirmed, would imply a strong dependence of the mixingscale below the formal Schwarzschild border, on the stellar mass orluminosity. Reproducing the features of the observed CMDs with standardvalues of envelope overshooting would require a metallicitysignificantly lower than the values measured in these galaxies.