Am I getting Poor performance from Deltec 410w monocrystalline panels (At 3 different sites) ?

[Leetpro]

Good day, has anyone else had any issues on the Deltec 410w monocrystalline panels ?

We have done solar systems at a few of our properties, accredited installers.
I do understand that there are losses but we are not even getting 50%-60% at max during full sun at the houses (mostly around 50% or less) with the Deltec panels.

All the installations are less than 4 months old, all less than 2 km from each other.

Site 1: Installed on a flat concrete roof, raised to about 30 degrees.
16 Deltec 410w panels (6560w) , 4 panels per string, 4 strings, Victron 250/100 mppt - max ever 3200watt , mostly 2500w

Site 2: Installed on a tiled roof, facing north.
12 Deltec 410w panels (4920w) , 4 panels per string, 3 strings, Victron 250/85 mppt - max ever 2500watt , mostly 2200w

Site 3: Installed on a tiled roof, facing north.
9 x Deltec 410w panels (3690w) 3 panels per sting, 3 strings, Victron 250/85 mppt - max ever 2200w, mostly 1800w

Now compared to site 4 and 5 with RenewSys 340w (330w?) panels 

Site 4:
20 x RenewSys 330w panels (6600w), 5 panels per string, 4 strings, Victron 250/100 mppt, max 5800w, mostly 4800w

Site 5:
20 x RenewSys 330w panels (6600w), 5 panels per string, 4 strings, Victron 250/100 mppt, max 5600w, mostly 4700w

Site 6:
Still in progress, Will be a Patio roof cover, at the same location as Site 4.
16 Deltec 410w panels (6560w) , 4 panels per string, 4 strings, Victron 250/100 mppt - Should be done early this week but I fear the power won't be close to Site 4 with the RenewSys panels.

I know people will sy angle, location, time of day ect but compared to the RenewSys the performance is almost half for the same wattage.
I did get the Deltec panels for a very good price and still have another 12 left, is there any way to get them tested before they are installed ?

Tia
 

[GreenFields]

What battery systems are connected? Any chance that the first 3 sites are operating in 24V mode?

[Leetpro]

no all the systems are 48v

freedom won batteries 

 

3 are Victron 15kva Quatro's

2 are Victron Multi plus 2 5kva