Root rot or what? Flowering stage

Hi guys, I think I'm having some probs with my babies.

They are 2 purple auto week 6 and 2 bubble kush auto in week 4.

All of them having issues with yellowing leaves, brown spots, burnt tips leaves.. yellowing starts from bottom leaves.
At the start I was thinking only they were hungry so I feeded with full strength nutes (I'm using biobizz nutes, so it's difficult having nuteburns right?)

Now, purple auto in week 6 responded well, but I'm really cutting off too much leaves... They take water in 4/5 days and I'm reading online that an auto in that stage should drink more often.

I recalibrated my pH tester to avoid pH probs, and stopped using pH down, also because I noticed that biobizz nutes don't need that: tap water (7.4) + biobizz nutes = 6.35 so it's ok!

biobozz soil LightMix
quantum board led 300w 15" distance from canopy
11L pots
temp and humidity are ok I think 65/75f and 30/55% ru

2 purple bud auto:

Temperature way too low for LED. Suggest raising it to over 80 during lights on. Consider feeding and the next time giving straight water. I’m not noticing any deficiency at this point and the leaves you took look more like from a fertilizer excess.

I'd agree that raising it to 80f+ would improve drinking rate.

Also, what's your floor like? If it's fir example a concrete floor that will keep your rootzone even colder .

Stop chopping leaves off, they are great for analysis, take em off without solving the issue and your just going to lose more

hotrodharley said:

Temperature way too low for LED. Suggest raising it to over 80 during lights on. Consider feeding and the next time giving straight water. I’m not noticing any deficiency at this point and the leaves you took look more like from a fertilizer excess.

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Thanks for your suggest. I have a try your suggestion.