HELP needed for beginner grow!

Hello Everyone,
1st time grower and poster to this forum. Have been trying to grow a couple plants that survived from about a dozen seeds. Have included pictures to hopefully help determine what I am doing wrong.

These plants have been growing for over two months, but have seemed to stop growing. Yesterday I noticed yellow tips which I assume may be nutrient burn…but not sure. Plants are under 24 hr light, I water and feed couple times a week, temp is around 73 degrees. I’ve switched from LED to CFL to Florescent lights with no noticeable growth.

Can anyone provide info on what I am doing wrong? Any assistance will be appreciated.

Wish I could but I got this chart on this site, hope it helps! .