Leaves are turning yellow with dead spots and wilting.

[Chieferl06]

Hello all! This is my first grow and first post on this forum. (Hopefully im doing this right.) Really hoping someone can help guide me in the right direction here.

DETAILS:
- GG#4 Autoflower feminized seeds from MSNL
- Fox farm happy frog soil/ 5 gal pots
- 6.5 weeks old from seed.
- Temps 68-80f/ Humidity 40-60%
- Sf-2000 LED light approx. 20-24" above canopy. 20/4 light schedule.
- Water between 6-6.8PH tested with digital meter
- No nutrients for the first 3 weeks. DynaGrow "Grow" nutes at 1/2 recommended dose every other watering starting at week 4. Also added 1/2 dose calmag with nutes.
- Watered with DynaGrow "Bloom" nutes (full dose) a few days ago basically just to see if it helped. It did not.
- Decided to flush soil with just PH'd plain water last night.
- Noticed bugs in the soil 2 weeks ago (turned out to be springbacks, fairly harmless from my research) and sprinkled diatomaceous earth on the soil to help get rid of them.
- Generally water every 2-3 days or when pot feels light. Did start watering slightly more frequently recently as it seemed like soil was drying out quicker. Usually water 1/2 to 3/4 of a gallon until i get a good amount of runoff out of the bottom of the pot.

Description: I started noticing some yellowing leaves about 1.5 weeks ago. They have been turning yellow and getting big dead sections. Seems to be starting at the lower older fan leaves although there are some in the "middle" of the plant starting to do the same. The top growth seems to be a pretty light color to me but im not exactly sure whats normal. As you can see in the picture one leaf didnt yellow at all but shrivled up and i plucked it off very easily. Ive been doing a ton of research but still cant pinpoint what this is or what the next steps i should take are. To me this looks like maybe a potassium issue? or am i over watering? Too much calmag? Nutrient lockout? I decided to flush the pot with regular water to hopefully get a fresh start.

The problem did seem to start shortly after using the diatomaceous earth on the soil.. can it do damage? From what i read it is ok to sprinkle on the soil.

[growell]

Start giving full nutes and calmag looks likes diffrent defiences u dont need to do run off in soil only when flushing i give nutes every feed and flush every so often your soils not holding on to anything mate hope this helps also u better off starting with femenised seeds u get more time to play around with autos no room for error

[Chieferl06]

Thanks for the advice. Will start giving full nutes and calmag. Thanks for that, i kept seeing advice that said to water until runoff every time...i dont know any better haha. i appreciate the help.

[MeEasy]

Looks to me like it could be in need of some nitrogen, alot of flower food is low in nitrogen which is right because they don't need alot but will eat the lower leaves. Plus the top of your plant is a lite green which is another sign it could be nitrogen deficiency. Here's a link to GWE plant dr check out the part on nitrogen and compare your plant to the pics. It's pretty normal later in life for em to eat their lower leaves but yours aren't there yet. DE won't hurt them it only works when it's dry though so you'll need to apply it more than once plus it doesn't kill eggs so bugs will probably come back

https://www.growweedeasy.com/cannabis-symptoms-pictures