Question about solar panels

[farmgirl]

Ok. Here is the situation. We have a 24 foot above ground pool with four 2x20 foot solar panels for heat. The panels are set up side by side, (joined together on the short ends) with inlet on one end of the hose linking all four panels at one end, and outlet on opposite end.

(from pool)----panel1----panel2----panel3----panel4-----(to pool return)


Sorry about the rough "sketch"...but i hope it gives some idea of the setup we have. Now, the problem is this. The pool is heating, and it seems that the two OUTER panels (#1 & #4) are working OK....they feel almost COLD to the touch, even in very hot sun. The 2 center panels (#2 & #3) always feel hot, and are not as heavy as the out panels, indicating to me that there is little if any water running thru them. DH says that the way he has it set up, if ONE panel is getting water flow, then they ALL HAVE to be getting water flow. I say that makes sense, but why are the panels not all the same weight and temperature? Our pump is a 1.5 HP 2 speed pump, but stays on "low" when the solar is running. Any input will be appreciated, as we have been arguing about this for over a year!