Need opinions on this...rootbound maybe?

Check these pics. These plants were planted on April 11th as seeds in soil.

You can see some yellowing and some curling which I am concerned about. I don't think its overwatering because I have only been watering them every 3 days and where I live is very very dry. I also use a moisture meter and make sure its reading very low before a water. You can see the moisture in the soil in these pics because I just watered them a few hours ago.

Anyways my theory is they are possibly root bound already? These pots I started them in are very small, only 3 and 1/2" tall or so.....

Looking for any advice here on whats causing the curling and yellow!!

overwater. mild nute burn. not enough light. PH. could be any of these or a combination i am assuming,

are those t5's?

No, I use a 400 watt HPS and 4 small T8's, light is not an issue.

For overwater, I water every 3rd day and as I said its very very dry here.

I used nutes once and it was extremely week but I think maybe its a mild nute burn...only thing I can think of really...

PH is fine, my water and runoff is 5.5 PH, soil is around 7..

Well I transplanted them last night and here is what they look like today. The yellowing continues and one of them is really curling.

Is it possible I need to give them nutes?

I am at a loss here...

anyone?