Is this normal in 4th week of flowering

Hi guys I am going into the 4th week of flowering. I am growing 2 white widow and 1 bagseed but I have noticed in the last 4 days the leaves are slowly starting to turn yellow. I went away for a week and the girlfriend took care of the plants for me but I have just discovered that when I picked up the pots they were over watered she was giving them 2 litres of water a day and they didn't need that much as I only watered them with 1 gallon of water every 3 days. Do you guys think the yellowing is due to her overwatering my plants? or do my plants look normal at this stage of flowering? What should I do everyone? all help is appreciated

P.s my strain is a 8week flowering strain/ Grown under 400watt hps.

1.Could they be root bound I dont think thats it cuz the plants are 2.2 feet with the smallest one being 1.8 feet and they are in 3gallon pots with the sativa bagseed in a 5 gallon.

2. Lack of nitrogen or magnesium

3. Overwatered

Here is the link to my journal:

https://www.rollitup.org/blogs/blog4621-normal-4-weeks-into-flowering.html

Overwatering can definitely cause you plants to yellow. Let them dry out a bit and then feed with some feed containing nitrogen.

Thats what I figured too. wait for them to dry and feed a bit of nitrogen. infact I was going to give it some tigerbloom with a small dose of calmag after it dries. thanks man