It looks like the hills adjacent to Casa Grande park are blocking your view toward South Mountain (Salt River Mountains) were the transmission towers are located. The elevation in the Arizona City area is about 1500' MSL. The peaks of the Casa Grande hills are over 2200' MSL. That means that you could build a 500' tower and still be blocked by terrain.
Click on the call sign of a station of interest in your TV Fool report and you will see a cross sectional view of the path profile.
KPPX-DT for example.
You are going to need a high gain combination antenna to see KPPX which is the lowest in strength. I would suggest the Antennas Direct XG91 and a Winegard YA-1713 joined with a Antennacraft 10G221 preamplifier. KNXV-DT is likely being effected by lower signal level, compared to your former location and I suspect, multipath. The higher gain and sharper directivity of the XG-91 is the best hope of overcoming both of those problems. Regardless of the obstructing terrain, a reasonable and safe effort to mount high and in the clear will likely offer a bit of signal improvement.
Antennas such as the Winegard HD7698P are a second best option in terms of gain on channel 51. The advantage of the Winegard would be one less antenna. But giving up 2 dB of gain when you are on the edge would risk making reception of KPPX less reliable.