At an indoor 75F dry bulb & 50% RH the indoor split should be close to 20F; I'd say @58% RH the indoor split ought to be near 17-F.
Possible refrigerant system problem;an overcharge would produce a false higher pressure reading than the actual heatload transfer would be providing. Therefore, we have to look at the outdoor split with caution...
The outdoor condenser split is on target using 50% RH but a little low using 58% RH; a higher latent/humidity load on the indoor coil increases the outdoor condenser split but decreases the indoor split.
The difference between the two splits indicates possible problems.
However, to pin point any problems we need the subcooling temperature & compressor amp-draw.
Using the Lennox Approach Method; for the 14ACX it calls for 6-F (+/- 1-F) of condenser subcooling. The liquid line temp minus outdoor ambient = approach subcooling temperature.
On non-accumulator Lennox A/C condensers with TXV metering devices the above method will indicate whether it's overcharged or undercharged according to their approach chart.