Help sick plants yellowing leaves and black spots

hi guys I'm really struggling to figure out what's wrong with my ladies I have 3 ww fems about 3months into veg outdoors in a small polycarbonate greenhouse they were going great until 1 of them started getting sick with black dots on most of the new growth and yellowing in all the fan leaves the fan leaves are green but shades of yellow come into them and eventually fully turn yellow and it's moved up started from the bottom, it seems they are about to go into flower as all the tops have tons of white hairs coming out of them some look sort of yellow hairs too.

 

Here's some pics of the plants/leaves you don't notice much of the leaves with black dots as I have removed them but they continue to return on new growth and old growth as you can see by the plant photos how much damage I have cut off

 

I had used chicken manure in my soil mix could I have over done it as I haven't used any liquid fertiliser in a few weeks now what.l can I do to resolve this?

 

Hi there thank you putting the effort to help me greatly appreciated, I will go out today and purchase some calmag from the droshop I'm only using tap water that's filled into buckets and left for a day in the open then fed to the ladies I thought this would be better to feed the plants rather then straight out of the tap.. I don't have a tester for my water levels but I will have one this week waiting for it to arrive, so you don't want me to trim the spotted leaves can I ask why not ? And will they recover if this cal mag works also do I feed cal mag to the roots or by foliar spray, I Foliar sprayed my girl with Epsom salts a tsp to a litre a few days ago and she looks to have improved not so much spots but still some there leaves look much more greener the new growth