Whats happening to my leaves :(

Hey guys been doing my first grow in hydro, currently 5-6 weeks into flower not gonna go into too much detail but quite a few of the leaves in on my plants have been looking a bit odd tried matching them up to the pictures of all sorts of defficiencies but its a bit hard i think thought id post a couple of pictures. Im thinking either nutrient burn or heat stress they still seem to be growing fine everyday tho and buds getting bigger, what should i do?

Bump ... help?

I think its quite normal for the bottom leaves turn yellow and fall off when you go into budding,
One of my plants look the same as yours but it still grows the same.
Newbie btw so don't just take my word as gospal, try and get one of the moderators they are always glad to help.

P3d1977

dont stop giving it N a lot of people make the mistake of switching to high flowering foods when in fact the plant still wants the same amount of N. Maybe instead of switching straight to flower nutes do a 50/50 or a 75/25, and follow the signs of your plant. deficiencies always start on bottom and work their way up. toxicities do it backward from the top. Not saying "give more nutes" just saying the high PK foods still requires N to carry through with the plants processes and most "bloom" foods arent the right ratios

I don't think it looks too bad... maybe a bit high nute strength knock it back a bit, the old girl will be fine.

okay guys bit more info to add,
It first started on the fan leaves near the top the biggest ones,
Its randomly hit other fan leaves too mainly the big ones
It hit the biggest plant first
Its starting to happen to the smaller ones too, random leaves kinda in random places so it kinda makes me dismiss heat.
Its starting to happen randomly to the new smaller leaves growing in the buds, only a few but a couple of rusty spots.

Ive totally cleaned reservoir and refilled with 1/3 strength nutes but im a bit scared of this because .... If it was a problem with over nuting wouldnt it have affected the smaller two plants first since its the same reservoir? (I may be totally wrong) (The big one is twice the size)
if it affected the big one first it automatically makes me think it could be a defficiancy, the only one that closely matches up is magnesium butt hen i look at more pictures and convince myself its not all the deficiancies look alike
Heres a picture of the worst affected leaf.

hard to see colour properly tho its sort of a copper colour

Oh yeah actually need to state this too.
I think this started when i started adding boost.
Basically my cousin had some IONIC boost. But i was using Hessi Bloom as my main nutrients. The guy in the hydro shop said it would be fine to use the ionic boost with the hessi bloom, and tbh so does the bottle of ionic say it can be used with any good bloom nutes.
But tbh it did kinda start happening when i started adding that...... thoughts please guys im getting really worried

bump help guys lol

Do you regularly flush your system?

Whats your ppm? Go ahead and tell me if your using a ppm meter for your hydro set up......

Looks like an N buildup. They look good, but a little on the dark green side, tips are burned, curling.