Is this phosphorous deficiency?

Hello this is my first grow and this white widow auto is at 7 weeks from breaking the surface of the ffof soil.

I gave tap water for 5 weeks. Then it started showing some dark spots that I thought looked like phosphorous deficiency. So i added 1 teaspoon per gallon of tiger bloom (half dose) and gave it food, water, food over a week long period.

It seemed like that stopped the dark spots from spreading but then I got 2 solid yellow leaves on the bottom of the plant. It looked like nitrogen deficiency from the pictures i saw. So i added 1/2 teaspoon of grow big and 1/2 teaspoon of tiger bloom to a gallon of water and fed that. The yellowing stopped but now the spots that i believe are phosphorous deficiency are back.

Im wondering if you think this looks like phosphorous deficiency or something else?

Also i see pictures right before harvest of plants with almost all yellow or withering leaves. So im wondering when to stop worrying about deficiencies and let the leaves get depleted?

Thank you for any help!

Oh yeah and for some reason this one plant seems to always have runoff ph between 6 and 6.2. Ive been watering with 7.0 for a while to bring it up but it doesnt seem to go above that.

yellow usually means lack of water or nitrogen. Purple is the phosphorus deficiency. I keep the nitrogen in the girls at all times. I limit it in flowering but still keep it in the system.