HELP , leaves turning yellow too fast

[Foxytelha]

Hey guys
this is week 5 of flower and the lower leaves are turning yellow too fast. Top leaves are ok still very green but the buds aren't fattening up although this is the worst strain ever ( Paraguayian weed) so thin buds were expected .
My question is , are those yellow leaves normal or maybe I have some issue or deficiencies ?
sorry for the lousy pictures I tried my best.
Thanks

[Flockshot]

With a general yellowing, starting at the bottom, it is classic nitrogen deficiency. Five weeks into flower, I wouldn't want to load the plant up with nitrogen, but I do think this grow needs a dose. Just my 2c.

[Californiakid]

I was thinking along thise lines as well. If it were me, some casting & compost tea would be in order.

[Californiakid]

Looks good to me !
What kind of soil and or nutrients are you using?
What size pot and how long was veg?

[Weed Pharma]

The yellowing at this phase is good and your plants are healthy and grow properly, showing a slight need of Cal/Mag - if you have some use it- if not don't worry.
Plants do not need much N and adding N could stunt the bud development.

The 5th week is always difficult as, they don't seem to grow as much and then in about 10 days you will see a massive increase in buds density.
The only nutrients you may want to consider is a dose of micronutrients.