Tomato seedling has purple leaves at the bottom?

[sunnyderder]

Hi everyone. My tomato seedlings, about 5 weeks old, have gotten purple at the underside of their leaves. They seem healthy otherwise. I haven't fertilized them, but the Miracle gro potting soil i used does have some fertilizer. Does anyone know what this is/why its happened? Pictures attached. Thanks in advance!

 

[Chuck]

They have a phosphorus deficiency. Fertilize NOW.

 

[sunnyderder]

Thanks Chuck. Thats what some googling also revealed. The weird thing is, they aren't always purple. In fact they were purple 2 days ago, then went back to normal, and now purple again today. Is this still a P deficiency?

 

[Chuck]

Thanks Chuck. Thats what some googling also revealed. The weird thing is, they aren't always purple. In fact they were purple 2 days ago, then went back to normal, and now purple again today. Is this still a P deficiency?

No. Has the humidity or the temperature changed?

 

[sunnyderder]

No. Has the humidity or the temperature changed?

nope! They are indoors, same location. It’s gotten a bit warmer over the last few weeks but they are indoors so nothing much has changed.

 

[Chuck]

nope! They are indoors, same location. It’s gotten a bit warmer over the last few weeks but they are indoors so nothing much has changed.

Beats me. If the new growth is still ok there isn't much to worry about.