Sudden problems after 6 weeks of perfect flowering

Hey,
Have a single plant grown with LST that has performed amazingly through veg and 6 weeks of flowering. It has tons of bud sites and nice large colas. I haven't had a spot of burn, stress or any other issue the entire grow. I've been feeding them the FF schedule but tend to feed lightly each watering rather than every other and it hasn't caused problems yet. No flush yet as I didn't seed a need to fix a problem I wasn't having. I always put in ph 6.4-6.7 (soil)

My last watering I upped the nutes a bit (still well under full strength) which is the only change I can recall making. This was also my third watering introducing Fox Farm Cha Ching. Either coincidentally or directly after my plant began exhibiting the following symptoms:

-light rust colored spotting and veins centralized on the canopy most directly under the light. This looked identical to what pictures of calcium deficiency looks like. The rust spots seem along the veins and they have since slowly started spreading to more deep green leaves. Originally the spots seemed centered on some leaves that were a bit bleached from the HPS but showed no signs of heat stress.

-at same time the plant began showing some purple traits on the sugar leaves of the buds, again centralized to the center most area that receives direct light. This seems abit too coincidental to just be genetic and suddenly occurring with the spots. It not exactly a full purple but instead more of a darkening.

my initial hunch was that due to having fed regularly and never flushed, I had some kind of salt buildup that was causing PH lockout of at very least calcium and possibly others to cause the leaf color shifts. I also wondered if possibly this was some form of nute burn due to me upping does on the last watering before problems. This doesn't look like classic nute burn, though.

So far what I've done is a flush of around 8 gallons of PH 6.5 water, followed by a light does of cal-mag and no other nutes.

Buds are nice and big but calyx haven't swollen yet. I'm assuming it has around 2-3 weeks left. Should I even bother attempting to address this issue at all? Should I just begin flushing each watering and completely stop nutes and let it finish? Normally I don't subscribe to starving my plants right as they swell but I'm unable to definitively diagnose this issue which has me worried I may exacerbate the issue by reintroducing heavy flowering nutes once again.

A picture would really help.

Sounds like you should continue, depending on how the plant look (if you suspect calcium-def, it's low PH, or nute inbalance, or lack of calcium in medium).
Too much Potassium will make it hard for the plant to get the Calcium.

Lack of calcium: weak stems, low tolerance to heat, bud development is slow, roots will be more suscepticle to root problems.

Sorry, but a picture would proably give you meaningful answers.

You fan leaves will start yellowing in flower.

Do you know your ppm on feedings and how often are you feeding? You are thinking about this the right way. Posting a picture will help get you more opinions.

If you only have a couple weeks to go, I would run some clearex or similar product through your pots to unlock the salts and get them out. I would not do a proper flush unless things start to go down hill fast.

If you have longer to go, I would still clear the pots with a clearing product and then cut your nutes in half from where they were and go water only last two weeks.

The Fox Farm feeding schedule can be two to three times too much for some strains of MJ.