Yellowing of leaves at 5weeks flowering.

try and put pick up so we can see

 

prob norm this happens cause most flowering ferts have very little nitrogen,they focus on phosphorus

 

plants are feedin' sucking up the sugar stored in those leaves....its normal during late flower...if plants look good otherwise your on your way to some sweet bud....keep up the good work.............deacon........ps...pic's would help

 

Outdoors plants that have access to nutrients still do it just means ur matureing happens to most strains,you get every color but green eventually

 

I agree. So long as your leaves are drying out and dying then this is the natural process of the plant focusing energy into flower production. I would recommend against feeding them heavily at this stage in flowering but a good organic flowering booster could be useful. A 250ml bottle of BioCanna BioBoost might make all the difference, but then again your plant will probably be just fine without it.

With a picture I'm not going to be concrete on my stance here but it sounds like everything is going good.