Auto pounder organic grow help

I have four auto pounders on the go using biobizz nutes and bio bizz light mix soil. They've been getting 2ml of grow up until week 3 then 2ml of grow and bloom since then. The leaves r turning lighter green and the tips are yellowing but only on one plant out of the four. It's hard to burn on organics so I'm thinking cal/mag def or low nitrogen. Confused please help. All others r fine one on the bottom left is the problem u can see the tips r yellowing.

back off on the nutes,use just ph'ed water for the next 2 waterings,nute burn for sure,autos dont need much food in the dirt,hope this helps

I'm not thinking nute burn>I think it's a nitrogen problem.I would flush it.then feed it a slightly heavier dose of nitrogen. Keep your other plants on the same feeding schedule as they are now.Make sure to ph after mixing you're nutes.

It can't be lack of nitrogen as all four r getting the same a out of nutes so all four would have the same problem at the same rates of growth. I'm thinking nute burn as the tips of the others have just started to yellow too. The first has been like that for a while over a week. The others have been fine till now.