Goji plants going yellow

[Digeroo]

I have about a dozen goji plants which I grew from seed last year.  Most have survived the winter but now some are looking rather yellow.  In fact they vary enormously from dark green to yellow and to tinged with red.   Was not expecting so much variation, they looked fairly similar last year except some have thorns.  Now the thorny ones are looking much healthier than the others. 

Any suggestions would be most welcome.

[Digeroo]

[mat]

photos would help.  yellowing can be different, for example is it yellowing from the veins, or from the edges?

Could be:
over watering
lack of nitrogen

The above two are the most common, but could also be:
lack of some trace element such as Mg (less common)
disease
pest damage

etc...

[goodlife]

I would give them good feed....Have you got any citrus feed...this normally have trace elements too..and I would scrape some surface compost off and top dress with fresh stuff..
Mine over wintered outside..some went into ground some were forgotten in pots..one in greenhouse.. ::)..and I only lost one..in pot outside...but they were in 2 litre pots.