Quadcopter descends even at full throttle!

I just recently switch to an apm 2.6 from a kk2.1 board for my quadcopter, with the apm board i have had a problem with the quadcopter descending even though i have throttle at full, this usually happens when i have executed a couple of flips (through ch 7) or when i switch between modes. After I have landed the quadcopter, i could rearm in stabilize and it fly it for several more minutes. This morning I was able to flip my quad 7 times and after the 7th it started to descend slowly to the ground and when i checked the battery it wasn’t even half gone!! My question is what might cause this and how might i fix this? I have included the log file from this morning please help and thank you!!

[attachment=1]2015-07-09 08-12-40.bin[/attachment]

My quadcopter build:

APM 2.6
alien 500 frame
4x Emax Mt2213 935kv 2212 Brushless Motor
Andoer Original Lion Power Lipo Battery 11.1V 3000Mah 25C MAX 40C
4x Neewer® 30A FIRMWARE Brushless ESC
carbon nylon 1045 props cw ccw
Neewer® APM PX4 Power Distribution Board with ESC Transfer Plate
gopro hero (no fpv yet)

total weight:
1179grams

[attachment=0]Capture.PNG[/attachment]

@Fadawar,
Here is an Auto Analysis of your dataflash log:

Size (kb) 198.5205078125
No of lines 3112
Duration 0:01:15
Vehicletype ArduCopter
Firmware Version V3.2
Firmware Hash c8e0f3e1
Hardware Type
Free Mem 0
Skipped Lines 0

Test: Autotune = UNKNOWN - No ATUN log data
Test: Balance/Twist = GOOD -
Test: Brownout = GOOD -
Test: Compass = GOOD - No MAG data, unable to test mag_field interference

Test: Dupe Log Data = GOOD -
Test: Empty = GOOD -
Test: Event/Failsafe = GOOD -
Test: GPS = GOOD -
Test: IMU Mismatch = UNKNOWN - No IMU log data
Test: Parameters = GOOD -
Test: PM = GOOD -
Test: Pitch/Roll = GOOD -
Test: Thrust = FAIL - Avg climb rate 8.74 cm/s for throttle avg 858
Test: VCC = GOOD -

Regards,
TCIII GM