Plant problem I.ding issue, possibly the ph?

Hey just wondering of anyone can help if the problems with my plants, I'm really new to this to please forgive any stupidity, I'm growing in a 90w (+ an additional 50w bulb ) led setup in soil. The younger plants in the picture are about 23days old whereas the older more mature plant is about 8/9 weeks. The growth on the younger ones has been stunted for the past 3/4 days while this problem has worsened. Can anyone help I.D the problem or confirm if it looks like ph damage an recommend a way to raise it? ( I'm currently waiting on a electronic ph meter to be delivered to check the level)

Ouch Id get them girls outta that soil rinse em off and start over..

Nute burn, almost positive. Is that a soil mix? Soil mixes tend to buffer the pH and come to an equilibrium at or around pH of 7, so pH is probably not your problem. If you confirm that it is nute burn, take a well rounded fertilizer and fertilize your plants at half dose. The remedy is in the fact that the soil solution will try to come to an equilibrium due to osmotic pressure giving your plant small doses of fertilizer it needs while flushing out the previous fertilizer.

Hope this helps. Try building a living soil (easier said than done), but this will lead to less pH and fertilizer issues.