possible deficiency/ lock up!?!?!

Hello Everybody,

Proud to finally be a member!!! On my second week of flowering outdoor one plant about 4 feet tall in an 18 g container, using MG potting soil (should have added some perlite) Top of plant looks beautiful some of the lower leaves are turning yellow and drying out and the fan leave stems on top turning purple. Started using sensi bloom last week only for 1 watering and used a 1/4 strength. I was told it could be a lock up or deficiency. its watering day tonite and not sure if i should continue with 1/4 strength(by the way i only use every other watering) or should i try another flush with just watering.

Any help would be great I hope i included everything Any questions please feel free to ask. This is my first mary!!!:jointsmile: