I wish I could help but these plants are looking bad. I wouldnt think its a ph problem theres really no spots all over the leaves. It does look like it may need some ferts the yellowing of the leaves. But also looks tremendously overwatered. How many times do you feed them plants. Are you letting the soil dry out? What kind of soil is that. Also these maggots you speak of are usually symphilids. Heres a little about them hope it helps.
Symphilids
Small pests that are tan to white colored and look like centipedes. They are very deadly to the plants, because they burrow down into the roots and damage them by feeding of them. Your plants leaves will begin to die off. They are found mostly in soil composites that have not been cleaned, like soil that has additives in them such as animal manure.
(I know it will smell funny but sterilizing the soil in the oven for 30 min can kill any pests in the soil, heat to 350 for 30 min.) They are easy to tell if you have them, because they come to the top soil when your plant is being watered, if you find you do have them, use Fungus Gnat Killer (“B.T." a non chemical,biological control) in the powdered form. One application should kill it, just to be safe repeat every 7 days to kill off the larvae. Tobacco juice kills them as well! And nematodes.
Picture 2 shows the Symphilids look like..
You should see these things crawl to the top of the soil when watering. Have you seen anything like this?