Yep 3.9 might be a deal breaker. For example, if the HLG-185H-C1400 can only put out 900-1000mA for 4 Vero29s in series, it is putting out less current than the HLG-185H-C1050 would AND the HLG-185H-C1050 can run 5 Vero29s.
One solution could be to use the HLG-185H-36A and run the 4 Veros in parallel. That way you will get about 1.38A to each Vero29 and the current can't runaway on you because you can set the max voltage screw at 37.5V, which would effectively limit the current to about 1.75A for a Vero29.