Quick question about heat stress

i have a 400 w light about 20 inches above a couple plants that are on their 4th nodes. my female is starting to brown from bottom up and the top nodes leaves are starting to get brown and twist. my ph is 5.9 in hydro dwc and i only have 2 ml of flora grow/micro/bloom in 10 gallons of water. i have a thermometer at the base of these plants and its showing around 75F. also i have a oscillating fan on them and no light is getting in the reservoir. the plants are about 3 1/2 to 4 inches tall (lowryder2) and its on the 5th week. am i not feeding enough? is the light too close? anyone got any ideas? one of my plants is looking really nice with no burns and hasnt showed preflowers yet but the female has started its pistils. im afraid ive over nuted them. but 2ml of each of those products in 10 gallons of water seems MILD ...really mild to me. like on life support almost. any help is appreciated!

That light sounds too close, look and check the top leaves, feel them are they dry and crispy to the touch? if so your drying them out which will stunt they growth and start to bring other problems.

to be honest if the light is 20cm above the plants , and they have fans on them then i doubt it is heat stress.

what worrries me most is that you have the same problem at the base of the plants working up the plant as it progresses.

temps and ph are ok.

sounds like nute burn as you suspected my friend. As you no doubt know cannabis burns easily indeed.

recommend that you halve your nutes for next feed or two and see how it goes.

good luck bud.

thanks for the help ill change the res today and im gonna put in about 1 ml instead of 2 i guess they cant starve if they got something

alright just changed the res, ph is 6.2 1 ml of general hydroponics grow micro and bloom, 1 plant hasnt showed sex yet and its looking really nice and its getting bushy starting its 5th node and its about 4 inches tall (lowryder2) my female is looking bad today, leaves are getting really brown but hasnt spread to the latest node that just showed up. the top node is under developed so far however so hopefully they wont get burned because i really dont want to lose this plant. i raised my lights up another 5 inches just incase. temp was 70, res temp is in the 50's and i sure hope they kick out of this funk.