advice on chop / diagnosing late flower nute burnout / deficiency THC bomb and White Widow autos

Hello, this is my first grow i am currently pretty late into the grow at 11 weeks total looking for advice on what to do atp. plants have been flowering for about 5.5-6 weeks (i got them from MSNL and the site says <8 weeks flower for white widow and 6-8 weeks flower for thc bomb). in the photos, the white widow in the one in the front (closest to door of tent) and the thc bombs are the two in the back. I can pretty easily tell the white widow is not as far along as it just has not put on as much weigh as the two thc bombs. I've been watering with the attached water schedule 2x per day to 25% runoff (i only water with nutes bc theyre in coco coir). I'm wondering if these look like i should start the one week flush now or in another week? trichomes look pretty clear all around but im just using a jewlers loupe and it can be a bit hard to tell. what i'm wondering is should i continue watering like normal for another week for two for the thc bombs / white widow / both or start the week long flush in a few days? and if so, should i make any alternations to the nute levels in the water or just repeat week 11 until theyre ready? Also the plants have what either appears to be a magnesium / potassium deficency as some colas have red stems or leaves that are yellowing / turning purplish with spots. the plants got some light burn around week 6 which is why some of the taller parts have some dryer leaves. also some of the stems are starting weighed down in parts where the buds are getting too heavy for the stems which indicates to me its getting closeish? I know people usually see things like nutrient burn etc towards the end of their grows due to buidlup or other things, but is this a out - of - the ordinary level situation where i should be worrying more bc bud quality will get compromised or something? any and all help / advice is greatly appreciated.