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The two recent gravitational-wave events GW190425 and GW190814 from the thirdobserving run of LIGO/Virgo have both a companion which is unexpected iforiginated from a neutron star or a stellar black hole, with masses$[1.6-2.5]~M_\odot$ and $[2.5-2.7]~M_\odot$ and merging rates $460^{+1050}_{-360} $ and $ 7^{+16}_{-6}$ events/yr/Gpc$^3$ respectively, at90\% c.l.. Moreover, the recent event GW190521 has black hole components withmasses 67 and $91~M_\odot$, and therefore lies in the so-calledpair-instability mass gap, where there should not be direct formation ofstellar black holes. The possibility that all of these compact objects arePrimordial Black Holes (PBHs) is investigated. The known thermal history of theUniverse predicts that PBH formation is boosted at the time of the QCDtransition, inducing a peak in their distribution at this particular massscale, and a bump around $30-50~M_\odot$. We find that the merging ratesinferred from GW190425, GW190521 and GW190814 are consistent with PBH binariesformed by capture in dense halos in the matter era or in the early universe. Atthe same time, the rate of black hole mergers around $30~M_\odot$ and ofsub-solar PBH mergers do not exceed the LIGO/Virgo limits. Such PBHs couldexplain a significant fraction, or even the totality of the Dark Matter, butthey must be sufficiently strongly clustered in order to be consistent withcurrent astrophysical limits.

GW190425, GW190521 and GW190814: Three candidate mergers of primordial black holes from the QCD epoch