Week 7 Autoflower, is this potassium deficiency??

[Luluboo80]

Hi! I am a total newbie to posting on forums and this is only my third indoor grow and only my third autoflower grow but I keep running into the same problems! I think this is a potassium deficiency but I really don’t know for sure and considering my first two grows were not great, I am worried the same is happening to this one!
This is the start of week 7 and I am feeding Biobizz grow, bloom, Algamic and calmag (as I am using very soft rain water). Growing in Biobizz light mix. Pineapple Express auto (fastbuds) 185w telos mesh led in 1 x 0.5 x 1.8 tent.
This grow is definitely going better than the first two as I have introduced calmag after they had huge calmag deficiencies but now something else is happening & I don’t know if it’s just a deficiency or lockout maybe?
I do think these plants are the smallest I have grown so far, for some reason & I don’t know why they haven’t stretched more in the last couple of weeks!
Now the bottom leaves are starting to get interveinal chlorosis, and I think some of the middle leaves too. Some at the bottom are turning very rapidly! I do think it’s a potassium def but I have looked at so many different pictures of deficiencies online that it’s now making my head spin as they all look so similar to each other!
Any help would be greatly appreciated!!

 

[LoveGrowingIt]

More information would be helpful. There are two reasons for apparent deficiency: Either there isn't enough nutrient, or the plant is unable to use the nutrients that exist. So...
What are the temperature and humidity (and VPD if you know it)?
How often do you water the plant?

 

[Luluboo80]

More information would be helpful. There are two reasons for apparent deficiency: Either there isn't enough nutrient, or the plant is unable to use the nutrients that exist. So...
What are the temperature and humidity (and VPD if you know it)?
How often do you water the plant?

Hi, thanks for replying! The temps are roughly 22-25 day and 19-21 night and humidity fluctuates but normally stays within 50-60%. I water every 2-3 days but I have wondered if this is possibly too often?