You say full sun but most likely is not given the morning sun. You also need to understand the load on the system to get a good panel output reading. Google "effects of shading on solar panels" etc.. Partial shading of even one cell may reduce its power output. Because all cells are connected in a series string, the weakest cell will bring the others down to its reduced power level. Much depends on how the panel was manufactured but lower cost panels will see the type of drop you are seeing. Also lower sun angle will greatly reduce the output. Solar cells also degrade over time. The panel rating is with direct overhead full sunlight no shade. I have 6 of the sun power cell flexible 100W panels mounted to the roof of my Campsite 21RBS. When I first installed my system I would see ~30Amps in full overhead sun. After a storm of with 3/4" hail stones I see a 20% degradation in my system. I can see some small dents in the panels plastic. I would not recommend these flexible panels. They are expensive per watt and IMO do not hold up. Doing some searches on Amazon I see many framed, more cost effective panels that will hold up to hail etc.