Undersized grounding
The main panel appears to have a nice fat braided ground on the ground rod.  

For the 60A subpanel and 50A A/C service, a 10 AWG ground wire is perfectly adequate.  Not seeing the problem. 

The 30A sub is a Zinsco, which some very serious fire-starting problems with its buses, which can't be fixed by swapping breakers.  Since it appears to be configured as a disconnect switch anyway, maybe you can replace it with that.  

I could do without the artiste "runt"-ing off all the wires to barely long enough to go where they're going right now.  You'll hate that guy if you ever have to put in GFCI or AFCI.