Day 52 autoflower, should leaves be falling off??

Hi all,
I'm at day 52 (7 weeks & 3 days) and I have had yellowing of some bottom leaves for a week or so but now they are really getting worse, to the stage that some of them have fell off. I'm also unsure if she's filling out as she should be, the buds are growing & forming trichomes but I think they maybe should be bigger.

Its my first grow so I'm not really sure about certain things, although I have done alot of research before starting.

I would hate for something to go really wrong at this late stage in the grow.

I have been using the wet & dry cycle for feeding which started off at once a week but is now every 4-5 days but she's also in twice the size pot that she started in (15ltr now)

I'll try & upload some pic's.
The couple of pic's of buds are from the side branches.
The hps has made the buds look a funny colour.

my lowest ones fall all the time and i just let it be. i just chalk it up to not enough light down below for them. but i also have 4 bushes packed into a tent so the lower sections are fairly shaded.

Not in my garden

Hi, thankyou for ur replys, do u have any suggestions as to what it could be RM3? As I say im new to all this, its my very first grow & I would really appreciate any input/ advice as it would be devastating for me for something to go badly wrong now.

I was wondering if a flush would do any good?

1st, a wet dry cycle doesn't sound right, you lettin em droop before you water?
2nd, I would guess your usin bloom nutes (I don't)
3rd, a flush might help but that could depend on what medium?

are you over feeding? those leaves look awfully green and the burns on thos lower leaves start at the edge out so possibly a little heavy on the N thats my guess.
and dont ever flush btw

Im using biobizz light mix, with biobizz grow 3ml/ltr & biobizz bloom 4ml/ltr, magna-cal 1ml/ltr, should i continue with the neuts at a lower dose maybe?

I have been using the wet/dry cycle & use her weight as a guide to feed her as well as feeling into the top couple of inches of soil.

Thankyou for all ur advice its very much appreciated.

I second the nutrient burn, those leaves are practically blue.