Yellowing of Lower Leaves

Hi does anyone have any idea why some of my leaves re going yellow? The yellow ones are also softer almost soggy.

I am about 3-4 weeks into flowering, growing the ultimate using canna aqua nutes in an nft and 600w hps light.

That's completely natural as the plant is using more Phosphorus and Potassium it's sucking everything out and putting it into big beautiful flowers for you!! I wouldn't worry at all about those at the bottom, some of the other fan leaves may start to yellow later in flowering as well.

thanks. a couple leaves at top are starting to do the same, I have upped the nutes a bit and was worried that this was the cause also the temps are a but high so just after lifting the light a few inch

dont forget N is still needed in flower.