Seedlings tips turning brown and dying

Hello folks.

This is my second indoor grow. I'm growing in soil under a 250w MH(aprox 22000 lumens).

I have 6 seedlings and 3 of them are showing brown tips going to the middle of the leaf. I can't figure out what the problem is. Maybe some of you more experienced individuals can.

The soil mix is something picked up locally, seemed good enough. I am using tap water with a PH of around 7,6. I know this is high and this is why tonight i added vinegar to the water to get the ph down(one teaspoon per gallon). I am currently not using any nutes because the babies are to young. I'm suspecting that my problem is either a high PH causing a nute lockout or nuteburn from the soil i'm using, altough on the bag it did not say that it was enriched. As a preventive measure i flushed my babies and currently i'm hoping for the best.

Please take a look at the pics and guide me through my problem. All advice is welcomed.

Cheers.

try and just water with 6.5 pH and should be fine

dont be doing too much at a time to those babies youll get stunted growth. Little at a time goes a long way, your in soil you should be able to salvage it if it gets a little worse

The soil is crap with weeds in it and this is causing the yellow lower leaves combines with the high ph. The brown tips you say youve got are from overwatering, that medium looks like a mudcake. Also what are you watering with? a fire hose? all the perlite blown out of the pot.

You should be fine. Just let the soil dry out a bit now. Then feed with your selected nute at 6.3-6.5 ph. Most nutes will bring donw the ph of the tap water. I believe my tap water is also around 7.6....7 something. When I add my nutes it drops to 6.3. I don't know if all water soluable nutes do that though.

The soil looks like this because i took the pics right after i flushed the pots. I'm watering once every 48 hours or even more than that. I usually wait for the top layer to get dry and the pot to get lighter. Thank you for your reply.

doesnt need that much water IMO

Could this be a phosphorus deficiency?